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  • 1.
    Amira, Sami
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Spångberg, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Derivation and evaluation of a flexible SPC model for liquid water2004In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 303, no 3, p. 372-334Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations of a new flexible water model are presented. The potential function is based on the simple point charge (SPC) model combined with an accurate experimental quartic intramolecular potential (CCL). This potential not only reproduces the key structural, dynamical and thermodynamical properties of liquid water, but also generates the correct values for both the absolute O–H vibrational frequency and the gas-to-liquid frequency shift. Thus, the model yields a value of ca. 3420 cm−1 for the peak maximum of the anharmonic OH stretching band for liquid water (experiment 3400 cm−1) and a corresponding gas-to-liquid downshift of −300 cm−1 (experiment −310 cm−1). The paper also emphasizes the importance of parameterizing correctly both the harmonic and anharmonic force constants in the gas-phase when developing flexible water models to be used in the liquid state.

  • 2.
    Andersson, LM
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Karlsson, Hans O
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Berg, Lars-Erik
    Beutter, Matthias
    Hansson, Tony
    Vibrational wave packet dynamics in NaK: The A (1)Sigma(+) state1999In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 241, no 1, p. 43-54Article in journal (Refereed)
    Abstract [en]

    A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier studies. The previous interpretations of the probe processes are revised. Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational period, and leads to excellent agreement with the experiments.

  • 3.
    Barklem, Paul S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Tscherbul, Timur V.
    Univ Nevada, Dept Phys, Reno, NV 89557 USA..
    Inelastic processes in atomic, molecular and chemical physics (in honour of Andrey K. Belyaev)2015In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 462, p. 1-2Article in journal (Other academic)
  • 4. Baryshnikov, Gleb V.
    et al.
    Sunchugashev, Dmitry A.
    Valiev, Rashid R.
    Minaev, Boris F.
    Ågren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications2018In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 513, p. 105-111Article in journal (Refereed)
    Abstract [en]

    An in-depth analysis of the vibronic absorption spectra for the recently synthesized blue-fluorescent OLED emitters bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3′,4′-h]anthracene has been carried out computationally at the density functional theory level within the Franck-Condon approximation. These molecules are characterized by extended and rich electronic absorption spectra with most absorption bands being of vibronic origin. The first excited singlet state of bis[(1,2)(5,6)]indoloanthracene compound demonstrates a clear observable double-peak vibronic progression for two different active modes in the absorption spectrum, while the S2 state is vibronically inactive. In contrast, for the larger biscarbazolo[3,4-a:3′,4′-h]anthracene compound the S0 → S2 transition demonstrates well-resolved intense vibronic bands which overlap the less intense progressions of few modes in the S0 → S1 transition. We have also found, that even the higher-lying and very intense S0 → S4 and S0 → S5 transitions for bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3′,4′-h]anthracene, respectively, are characterized by clear vibronic progressions in excellent agreement with experimental spectra.

  • 5.
    Bhattacharjee, Satadeep
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Banerjee, Rudra
    Wende, Heiko
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Electronic structure of Co-phthalocyanine calculated by GGA plus U and hybrid functional methods2010In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 377, no 1-3, p. 96-99Article in journal (Refereed)
    Abstract [en]

    Electronic structure calculations have been performed for the Co-phthalocyanine molecule using density functional theory (DFT) within the framework of Generalized Gradient Approximation (GGA). The electronic correlation in Co 3d orbitals is treated in terms of the GGA+U method in the framework of the Hubbard model. We find that for U = 6 eV, the calculated structural parameters as well as the spectral features are in good agreement with the experimental findings. From our calculation both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are dominated by the pyrrole carbon, with a HOMO-LUMO gap of about 1.4 eV. The GGA+U results obtained with U = 6 eV compare reasonably well with the calculations performed using Gaussian basis set and hybrid functionals in terms of ground state geometry, spin state and spectral features. The calculated valence band photoemission spectrum is in quite good agreement with the recently published experimental results.

  • 6. Coriani, S.
    et al.
    Stener, M.
    Decleva, P.
    Holland, D. M. P.
    Potts, A. W.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    A study of the valence shell electronic structure and photoionisation dynamics of s-triazine2015In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 450, p. 115-124Article in journal (Refereed)
    Abstract [en]

    A joint experimental and theoretical approach has been used to study the valence shell electronic structure and photoionisation dynamics of s-triazine (1,3,5-triazine). Synchrotron radiation has been employed to record angle resolved photoelectron spectra of the complete valence shell for photon energies between 17.5 and 100 eV, thereby allowing photoelectron anisotropy parameters and branching ratios to be determined. Absolute photoionisation partial cross sections have been estimated as the product of these branching ratios and the absolute photoabsorption cross section. The Kohn-Sham and the time-dependent version of density functional theory methods have been used to calculate photoelectron anisotropy parameters and photoionisation partial cross sections, and these have been compared with the corresponding experimental data. The calculations predict that shape resonances affect the photoionisation dynamics of several of the molecular orbitals. The angle resolved photoelectron spectra suggest that the 1a(2)''(pi) orbital is more tightly bound than the 5e'(sigma) orbital, and that the 4a(1)'(sigma) orbital is more tightly bound than the 1a(2)'(sigma) orbital, in agreement with the predicted molecular orbital sequence. For the outer valence orbitals the single-particle picture of ionisation holds but electron correlation becomes increasingly important for the inner valence 4e', 3e' and 3a(1)' orbitals and leads to a redistribution of intensity. Instead of a readily distinguishable main-line, associated with each of these orbitals, the photoelectron intensity is spread over numerous satellite states and the resulting band is broad and featureless. 

  • 7. Edvardsson, D.
    et al.
    Danielsson, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eland, J. H. D.
    An experimental and theoretical investigation of the valence double photoionisation of the IC molecule2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 332, no 2-3, p. 249-254Article in journal (Refereed)
    Abstract [en]

    The double valence photoelectron spectrum of ICl has been measured at two photon energies,303.78 angstrom and 379.3 angstrom, by the TOF-PEPECO technique. Relativistic molecular electronic structure calculations have been performed for electronic states connected to the three lowest groups of dissociation limits to support the interpretation, and vibrational constants have been calculated for the quasi-bound states. The two lowest double ionisation energies are found to be 27.45 +/- 0.1 eV (vertical) and 27.69 +/- 0.1 eV (vertical). They are associated with the X-3 Sigma(-)(0.1), electronic states of ICl2+, respectively, which are the only states predicted to be stable by the calculations. The two following states connected to the same configuration are in order a (1)Delta(2), and b (1)Sigma(+)(0). The double ionisation processes building up the spectrum are found to be mainly direct, and energies and widths of the bands are well reproduced by the calculations.

  • 8. Edvardsson, D
    et al.
    Danielsson, A
    Karlsson, L
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
    Eland, J H D
    An experimental and theoretical investigation of the valence double photoionisation of the iodine molecule2006In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 324, no 2-3, p. 674-678Article in journal (Refereed)
    Abstract [en]

    The double photoionisation spectrum of molecular iodine has been measured at three wavelengths by the TOF-PEPECO technique and is interpreted using relativistic molecular structure COSCI calculations of potential curves for a large number of electronic states connected to the three lowest groups of dissociation limits. The lowest double ionisation energy is 24.85 ± 0.02 eV (adiabatic) or 24.95 ± 0.02 eV (vertical). It is associated with the electronic state of . The double ionisation process is mainly direct, and positions and widths of the bands are well reproduced by the calculations.

  • 9.
    Edvardsson, D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eland, J.H.D.
    University of Oxford.
    An experimental and theoretical investigation fo the valence double photoionisation of the iodine molecule2006In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 324, no 2-3, p. 674-678Article in journal (Refereed)
  • 10.
    Edvardsson, D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eland, J.H.D.
    University of Oxford.
    An experimental and theoretical investigation of the valence double photoionisation of the ICl molecule2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 332, no 2-3, p. 249-254Article in journal (Refereed)
  • 11.
    Edvinsson, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Pschirer, Niel
    Schöneboom, Jan
    Eickemeyer, Felix
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Photoinduced electron transfer from a terrylene dye to TiO2: Quantification of band edge shift effects2009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 357, no 1-3, p. 124-131Article in journal (Refereed)
    Abstract [en]

    A terrylene chromophore exhibiting a high extinction coefficient has been developed as a sensitizer for photovoltaic applications. The photophysical and photochemical properties of the dye were analyzed both experimentally and theoretically. Terrylene-sensitized nanocrystalline TiO2 solar cells yielded good photocurrents providing more than 60% in external quantum efficiency. The photoinduced electron transfer from the dye to TiO2 was found to be very sensitive to conduction band edge shifts in TiO2 induced, either by changes in the composition of the redox electrolyte or by UV-illumination. This sensitivity was observed in quantum efficiencies for photocurrent generation of terrylene-sensitized solar cells and in photoinduced absorption experiments. The conduction band shifts were quantified using charge extraction methods. The observed sensitivity of the injection efficiency suggests that photoinduced electron transfer occurs from the relaxed excited state, possibly due to poor electronic coupling between TMIMA excited states and TiO2 conduction band states.

  • 12.
    Farahani, Pooria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ab initio quantum mechanical calculation of the reaction probability for the Cl- + PH2Cl -> ClPH2 + Cl- reaction2013In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 425, p. 134-140Article in journal (Refereed)
    Abstract [en]

    The SN2 substitution reactions at phosphorus play a key role in organic and biological processes. Quantum molecular dynamics simulations have been performed to study the prototype reaction Cl-+PH2ClClPH2+Cl-, using one and two-dimensional models. A potential energy surface, showing an energy well for a transition complex, was generated using ab initio electronic structure calculations. The one-dimensional model is essentially reflection free, whereas the more realistic two-dimensional model displays involved resonance structures in the reaction probability. The reaction rate is almost two orders of magnitude smaller for the two-dimensional compared to the one-dimensional model. Energetic errors in the potential energy surface is estimated to affect the rate by only a factor of two. This shows that for these types of reactions it is more important to increase the dimensionality of the modeling than to increase the accuracy of the electronic structure calculation.

  • 13.
    Fasshauer, Elke
    et al.
    Univ Tromsø, Dept Chem, Ctr Theoret & Computat Chem, Tromsø, Norway.
    Förstel, Marko
    Max Planck Inst Plasma Phys, Garching, Germany; Tech Univ Berlin, Inst Opt & Atomare Phys, Berlin, Germany.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Max Planck Inst Plasma Phys, Garching, Germany.
    Anion, Tiberiu
    Max Planck Inst Plasma Phys, Garching, Germany; DESY, Ctr Free Electron Laser Sci, Hamburg, Germany.
    Hergenhahn, Uwe
    Leibniz Inst Surface Modificat, Leipzig, Germany; Max Planck Inst Plasma Phys, Greifswald, Germany.
    Theoretical and experimental investigation of Electron Transfer Mediated Decay in ArKr clusters2017In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 482, p. 226-238Article in journal (Refereed)
    Abstract [en]

    We investigate the electronic decay of an Ar 3s(-1) vacancy in medium sized ArKr clusters. The only energetically accessible, radiationless decay mechanism is Electron Transfer Mediated Decay Three (ETMD3). Here, the argon vacancy is filled by an electron from one krypton atom, and the excess energy is transferred to a second krypton atom which consequently emits an electron. For the theoretical calculation of ETMD3 spectra, in a bottom-up approach, we study the dependence of the decay width on the geometry of elementary sets of three atoms, from which any cluster can be composed. We simulate the ETMD3 spectra of medium sized ArKr clusters and compare the resulting spectra to experimental ETMD electron spectra presented earlier (Forstel et al, 2011) and in this work. We show that ETMD3 is the dominating relaxation mechanism for the cases studied here. Experimental secondary electron spectra from ArKr clusters are compared to pure Ar and pure Kr clusters.

  • 14.
    Fasshauer, Elke
    et al.
    Arctic Univ Norway, Ctr Theoret & Computat Chem, Dept Chem, Univ Tromsø, Tromsø, Norway.
    Förstel, Marko
    Max Planck Inst Plasma Phys, Garching, Germany; Tech Univ Berlin, Inst Opt & Atomare Phys, Berlin, Germany.
    Mucke, Melanie
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Max Planck Inst Plasma Phys, Garching, Germany.
    Arion, Tiberiu
    Max Planck Inst Plasma Phys, Germany; DESY, Ctr Free Electron Laser Sci, Hamburg, Germany.
    Hergenhahn, Uwe
    Leibniz Inst Surface Modificat, Germany; Max Planck Inst Plasma Phys, Greifswald, Germany.
    Corrigendum to “Theoretical and experimental investigation of Electron Transfer Mediated Decay in ArKr clusters” [Chem. Phys. 482 (2017) 226–238]2018In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 501, p. 138-138Article in journal (Refereed)
  • 15.
    Hedin, L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Eland, J. H. D.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Feifel, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Soft X-Ray Physics.
    Cationic Rydberg states observed in resonantly enhanced electron spectra of CS22009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 355, no 1, p. 55-61Article in journal (Refereed)
    Abstract [en]

    The inner valence electron spectrum of the CS2 Molecule has been investigated in the binding energy range between 18.6 and 26.3 eV using synchrotron radiation for ionisation. Photon energies in the range from 67 to about 167 eV have been used, with particular focus on 166.70, 166.89 and 167.09 eV for which S2p electrons are resonantly transferred into Rydberg orbitals close to the ionisation threshold. From there, autoionisation takes the molecule into various cationic states characterized by two valence holes and a Rydberg spectator electron. Many new bands are observed which contain vibrational progressions with spacings around 120 meV in most cases. These are assigned as excitations of the totally symmetric stretching v, mode in the cationic state. The new bands reflect states in the cation that are close to the electronic states of the dication and assignments are made by comparison to double ionisation electron spectra.

  • 16.
    Hedin, Lage
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Tashiro, M.
    Linusson, P.
    Eland, John H. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ehara, M.
    Ueda, K.
    Zhaunerchyk, Vitali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Single site double core level ionisation of OCS2014In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 439, p. 111-116Article in journal (Refereed)
    Abstract [en]

    Single site O1s, C1s and S2p double ionisation of the OCS molecule has been investigated using a magnetic bottle multi-electron coincidence time-of-flight spectrometer. Photon energies of 1300, 750 and 520 eV, respectively, were used for the ionisation, and spectra were obtained from which the double core ionisation energies could be determined. The energies measured for 1s double ionisation are 1172 eV (O1s(-2)) and 659 eV (C1s(-2)). For the S2p double ionisation three dicationic states are expected, P-3, D-1 and S-1. The ionisation energies obtained for these states are 373 eV (P-3), 380 eV (D-1) and 388 eV (S-1). The ratio between the double and single core ionisation energies are in all cases equal or close to 2.20. Auger spectra of OCS, associated with the O1s(-2), C1s(-2) and S2p(-2) dicationic states, were also recorded incorporating both electrons emitted as a result of the filling of the two core vacancies. As for other small molecules, the spectra show an atomic-like character with Auger bands located in the range 480-560 eV for oxygen, 235-295 eV for carbon and 100-160 eV for sulphur. The interpretation of the spectra is supported by CASSCF and CASCI calculations. The cross section ratio between double and single core hole creation was estimated as 3.7 x 10(-4) for oxygen at 1300 eV, 3.7 x 10(-4) for carbon at 750 eV and as 2.2 x 10(-3) for sulphur at 520 eV. 

  • 17.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    COORDINATION EFFECTS ON THE STRETCHING VIBRATION OF THE OH- ION1993In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 170, no 2, p. 177-184Article in journal (Refereed)
    Abstract [en]

    IR and Raman measurements on crystalline hydroxides reported in the literature have shown that both frequency upshifts and downshifts with respect to the free-ion frequency occur. Here the fundamental stretching vibrational frequency of a bound OH- ion in different point charge environments has been examined by ab initio calculations at the MP2 level. For a given geometry of a q+ . OH- . q- complex, the ab initio frequency is found to vary in a systematic way as the electric field is increased: the frequency increases, passes through a maximum and then decreases. Both the value of the maximum frequency and the field strength at which it occurs are highly dependent on the geometry of the complex. Only the field component parallel to the OH- axis is effective in changing the OH frequency. The arc-like shape of the frequency versus field correlation curves ''explains'' the large degree of non-additivity found for the environment-induced frequency shifts. H-bonds donated by the OH- ion may, or may not, lead to a frequency downshift, depending on the other neighbours present. It is also shown that a model which explicitly takes the field inhomogeneity into account (by a simple polynomial in E(parallel-to), (E(parallel-to))2, E(parallel-to)', (E(parallel-to)')2 and cross-terms, evaluated at two different ''probing sites'' in the ion), manages to represent the OH- frequency shift for an ''arbitrary'' point-charge environment.

  • 18.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    FROM CLUSTER TO CRYSTAL - ABINITIO CALCULATIONS OF THE OH- FREQUENCY IN LITHIUM HYDROXIDE MONOHYDRATE1992In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 159, no 1, p. 67-73Article in journal (Refereed)
    Abstract [en]

    The fundamental O-H stretching frequency of the OH- ion in crystalline LiOH.H2O has been calculated by ab initio methods at the MP2 level. The experimental and calculated wavenumbers are 3575 and 3602 cm-1, respectively. This frequency is shown to result from a delicate balance of several important interactions between the OH- ion and its surroundings: the two cations in the (Li+)2.OH- cluster produce an upshift of 75 cm-1 with respect to the isolated ion, while the whole nearest-neighbour cluster, (Li+)2(H2O)2.OH-.OH-, gives a frequency downshift of -570 cm-1. The crystal field outside the nearest-neighbour cluster produces an upshift of 610 cm-1. This behaviour conforms well with the frequency versus field correlation curves calculated for simple hydroxide point charge complexes.

  • 19.
    Herschend, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Baudin, Micael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    CO adsorption on CeO2(110) using hybrid-DFT embedded-cluster calculations2006In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 328, no 1-3, p. 345-353Article in journal (Refereed)
    Abstract [en]

    The adsorption of CO on the CeO2 (110) surface has been studied using hybrid density functional theory (DFT) in the form of the B3LYP functional. In our calculations, both physisorption and chemisorption are observed. In the physisorption case, CO binds perpendicularly to a surface Ce ion. The adsorption energy is estimated to 0.1 eV and the CO stretching vibration becomes slightly blue-shifted (+9 cm(-1)), but the changes to the substrate and adsorbate structure are minimal. Test calculations using Moller-Plesset perturbation theory to the second order (MP2) suggest that dispersive interactions may be important in the case of CO physisorption on ceria. A chemisorption site was also found, where the CO molecule binds to two surface O ions, forming a surface carbonate species. Here, B3LYP predicts an adsorption energy of 2.1 eV and a red-shift of 470 cm(-1) for the CO stretching vibration.

  • 20. Holland, D. M. P.
    et al.
    Potts, A. W.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Zaytseva, I. L.
    Trofimov, A. B.
    Schirmer, J.
    A study of the valence shell electronic structure of uracil and the methyluracils2008In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 353, no 1-3, p. 47-58Article in journal (Refereed)
    Abstract [en]

    The valence shell photoelectron spectra of uracil, 1-methyluracil and 6-methyluracil have been studied experimentally and theoretically. Synchrotron radiation has been used to record spectra at photon energies of 40 and 80 eV. Photoelectron angular distributions have been determined and these provide an experimental means of distinguishing between sigma- and pi-type orbitals. Vertical ionization energies and spectral intensities have been evaluated using the many-body Green's function approach, thereby enabling theoretical photoelectron spectra to be derived. The calculated spectra display a satisfactory agreement with the experimental data and this has allowed most of the photoelectron bands to be assigned. Two of the outer-valence vertical ionization energies are similar to one another and the vibrational progressions associated with these transitions overlap strongly. Vibronic interaction between these states, induced through the excitation of out-of-plane vibrational modes, may lead to nonadiabatic effects. Preliminary theoretical investigation of this interaction has been performed.

  • 21. Holland, D. M. P.
    et al.
    Potts, A. W.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Zaytseva, I. L.
    Trofimov, A. B.
    Schirmerr, J.
    A study of the valence shell electronic structure of the 5-halouracils2008In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 352, no 1-3, p. 205-216Article in journal (Refereed)
    Abstract [en]

    Valence shell photoelectron spectra of the 5-halouracils have been recorded using synchrotron radiation at photon energies of 40 and 80 eV. Photoelectron angular distributions have been determined and these provide an experimental means of deducing the extent to which the molecular orbitals possess predominantly sigma, pi or halogen np character. In chloro-, bromo- and iodouracil two peaks, associated with the essentially halogen atom lone-pair orbitals, have been observed. The separation between these peaks, and the value of their photoelectron asymmetry parameters at an excitation energy of 40 eV, are compared with results for the corresponding orbitals in the halobenzenes and halothiophenes. Vertical ionisation energies and spectral intensities have been evaluated using the many-body Green's function approach, thereby enabling theoretical spectra to be derived. Assignments have been proposed for most of the structure observed in the valence shell photoelectron spectra based upon the available experimental and theoretical evidence.

  • 22. Holland, D. M. P.
    et al.
    Potts, A. W.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Stener, M.
    Decleva, P.
    A study of the valence shell photoionisation dynamics of pyrimidine and pyrazine2011In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 390, no 1, p. 25-35Article in journal (Refereed)
    Abstract [en]

    The complete valence shell photoelectron spectra of pyrimidine and pyrazine have been recorded with synchrotron radiation and the observed structure has been interpreted with the aid of vertical ionisation energies and relative spectral intensities calculated using time-dependent density functional theory. The theoretical predictions for the single-hole ionic states due to outer valence shell ionisation agree satisfactorily with the experimental results. Ionisation from the inner valence orbitals is strongly influenced by many-body effects and the intensity associated with a particular orbital is spread amongst numerous satellites. Photoelectron angular distributions and partial cross sections have been determined both experimentally and theoretically, and demonstrate that shape resonances affect the valence shell photoionisation dynamics. In addition to shape resonances occurring a few eV above the ionisation threshold, the calculations indicate that many of the orbitals are influenced by shape resonant processes at much higher energies. Some of these higher energy resonances have been confirmed through a comparison between the relevant theoretical and experimental photoelectron asymmetry parameters. The spectral behaviour of asymmetry parameters associated with pi-orbitals has been shown to differ from that of asymmetry parameters associated with sigma-orbitals. These differences provide a means of distinguishing between the two types of orbitals even in heavily congested regions of the photoelectron spectrum suffering from band overlap.

  • 23. Holland, D. M. P.
    et al.
    Powis, I.
    Trofimov, A. B.
    Bodzuk, I. L.
    Soshnikov, D. Yu.
    Potts, A. W.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    A study of the valence shell electronic structure and photoionisation dynamics of ortho-dichlorobenzene, ortho-bromochlorobenzene and trichlorobenzene2015In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 448, p. 61-75Article in journal (Refereed)
    Abstract [en]

    The valence shell electronic structure and photoionisation dynamics of ortho-dichlorobenzene, ortho-bromochlorobenzene and trichlorobenzene have been investigated both experimentally and theoretically. Angle resolved photoelectron spectra of ortho-dichlorobenzene have been recorded using synchrotron radiation in the photon energy range from close to threshold to 100 eV. The photoelectron anisotropy parameters derived from these spectra have been compared to predicted values obtained with the continuum multiple scattering approach. The comparison demonstrates that ionisation from some of the orbitals is influenced by the Cooper minimum associated with the chlorine atom. High resolution photoelectron spectra of the outer valence orbitals of ortho-dichlorobenzene and ortho-bromochlorobenzene have been recorded with HeI radiation and the observed structure has been interpreted using calculated ionisation energies and spectral intensities. Electron correlation affects ionisation of the inner valence orbitals and leads to satellite formation. Simulations of the (X) over tilde B-2(1), (A) over tilde (2)A(2) and (B) over tilde B-2(2) state photoelectron bands in ortho-dichlorobenzene have enabled most of the vibrational progressions appearing in the experimental spectrum to be assigned. Photoelectron spectra of trichlorobenzene have also been measured and the anisotropy parameters associated with some of the outer valence orbitals exhibit a photon energy dependence which resembles that predicted for atomic chlorine. This behaviour is consistent with the theoretically predicted character of these orbitals.

  • 24.
    Karnahl, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Kuhnt, Christian
    Heinemann, Frank W.
    Schmitt, Michael
    Rau, Sven
    Popp, Juergen
    Dietzek, Benjamin
    Synthesis and photophysics of a novel photocatalyst for hydrogen production based on a tetrapyridoacridine bridging ligand2012In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 393, no 1, p. 65-73Article in journal (Refereed)
    Abstract [en]

    Molecular photocatalysts allow for selectively tuning their function on a molecular level based on an in-depth understanding of their chemical and photophysical properties. This contribution reports the synthesis and photophysical characterization of the novel molecular photocatalyst [(tbbpy)(2)Ru(tpac)PdCl(2)](2+) RutpacPd (with tpac = tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2''',3'''-j]acridine) and its mononuclear building block. Furthermore, detailed photocatalytic activity measurements of RutpacPd are presented. The introduction of the tpac-ligand into the molecular framework offers a potential route to reduce the impact of water as compared to the well-studied class of RutpphzPd (with tpphz = tetrapyrido[3,2-a:2',3'-c:300,2 ''-h: 2''',3'''-j] phenazine) complexes. The distinct impact of water on the electron-transfer processes in tpphz-ligands stems from the possibility of water to form hydrogen bonds to the phenazine nitrogen atoms and will potentially reduced when replacing the phenazine by the acridine unit. The effect of this structural variation on the catalytic properties and the underlying ultrafast intramolecular charge transfer behavior will be discussed in detail.

  • 25. Kropacheva, Tatyana
    et al.
    Feikema, Onno
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Feyziyev, Yashar
    Styring, Stenbjörn
    Hoff, Arnold
    Quinone-induced high-spin state of cytochrome b559 in photosystem II2003In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 294, p. 471-482Article in journal (Refereed)
  • 26. Luo, Y
    et al.
    Cheng, YD
    Maripuu, R
    Seibt, Wolfgang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Öhlund, L
    Ejeklint, P
    Carman, B
    Xing, KZ
    Achiba, Y
    Siegbahn, K
    Highly excited states of nitric oxide studied by high-resolution resonance-enhanced multiphoton ionization spectroscopy1991In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 153, p. 473-481Article in journal (Refereed)
  • 27.
    Magnuson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Yang, L
    Guo, JH
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Såthe, Conny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Agui, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Luo, Y
    Ågren, H
    Johansson, N
    Salaneck, WR
    Horsburgh, LE
    Monkman, AP
    The electronic structure of poly(pyridine-2,5-diyl) investigated by soft X-ray absorption and emission spectroscopies1998In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 237, no 3, p. 295-304Article in journal (Refereed)
    Abstract [en]

    The electronic structure of the poly-pyridine conjugated polymer has been investigated by resonant and non-resonant inelastic X-ray scattering and X-ray absorption spectroscopies using synchrotron radiation. The measurements were made for both the carbon and nitrogen contents of the polymer. The analysis of the spectra has been carried out in comparison with molecular orbital calculations taking the repeat-unit cell as a model molecule of the polymer chain. The simulations indicate no significant differences in the absorption and in the non-resonant X-ray scattering spectra for the different isomeric geometries, while some isomeric dependence of the resonant spectra is predicted. The resonant emission spectra show depletion of the π electron bands in line with symmetry selection and momentum conservation rules. The effect is most visual for the carbon spectra; the nitrogen spectra are dominated by lone pair n orbital emission of σ symmetry and are less frequency dependent.

  • 28.
    Molloy, R.D.
    et al.
    University of Oxford.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eland, J.H.D.
    University of Oxford.
    Double photoionisation spectra of small molecules and a new empirical rule for double ionisation energies2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 335, no 1, p. 49-54-Article in journal (Refereed)
  • 29. Molloy, Ryan D.
    et al.
    Danielsson, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eland, John H. D.
    Double photoionisation spectra of small molecules and a new empirical rule for double ionisation energies2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 335, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    Complete double photoelectron spectra are presented for 18 small molecules where the location of charges in the cations and dications is relatively clearly defined. The data demonstrate the importance of a coulombic repulsion contribution to the double ionisation energies. Examination of data for a wide range of molecules leads to a new empirical rule to calculate double ionisation energies from the molecules' single ionisation energies and maximum dimensions. Where single and double ionisation energies are known the rule allows the deduction of plausible intercharge distances.

  • 30.
    Müller, Carsten
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Paulus, Beate
    Freie Universität Berlin, Physikalische und Theoretische Chemie.
    Electron correlation contribution to the N2O/ceria(111) interaction2009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 362, no 3, p. 91-96Article in journal (Refereed)
    Abstract [en]

    We have investigated the electron correlation contribution to the interaction energy of the N2O/ceria(111) system at the CCSD(T) level. N2O binds either with the N-end towards the surface with an interaction energy = -0.23 eV or with the O-end with = -0.27 eV. In the former case almost the entire binding energy is due to electron correlation effects, in the latter these effects contribute with about 60%. Analyses of the interaction energy contributions show that mostof the electron correlation part originates from the interaction of N2O with the O ions in the topmost surface layer.

  • 31.
    Nilsson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Alderborn, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Water-induced charge transport in tablets of microcrystalline cellulose of varying density: Dielectric spectroscopy and transient current measurements2003In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 295, no 2, p. 159-165Article in journal (Refereed)
    Abstract [en]

    Room temperature dielectric frequency response data taken over 13 decades in frequency on microcrystalline cellulose (MCC) tablets of varying density are presented. The frequency response shows on three different processes: the first one is a high-frequency relaxation process whose magnitude increases and reaches a plateau as the tablet density increases. This process is associated with orientational motions of local chain segments via glycosidic bonds. The second relaxation process, related to the presence of water in the MCC matrix, is insensitive to changes in tablet density. At lower frequencies, dc-like imperfect charge transport dominates the dielectric spectrum. The dc conductivity was found to decrease with increasing tablet density and increase exponentially with increasing humidity.

    Transient current measurements indicated that two different ionic species, protons and OH ions, lied behind the observed conductivity. At ambient humidity of 22%, only one in a billion of the water molecules present in the tablet matrix participated in long range dc conduction. The diffusion coefficient of the protons and OH ions were found to be of the order of 10−9 cm2/s, which is the same as for small salt building ions in MCC. This shows that ionic drugs leaving a tablet matrix may diffuse in the same manner as the constituent ions of water and, thus, elucidates the necessity to understand the water transport properties of excipient materials to be able to tailor the drug release process from pharmaceutical tablets.

  • 32. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    THE OH STRETCHING FREQUENCY IN LICLO4-BULLET-3H2O(S) FROM ABINITIO AND MODEL POTENTIAL CALCULATIONS1992In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 161, no 1-2, p. 87-98Article in journal (Refereed)
    Abstract [en]

    The "in-crystal" frequency of the anharmonic and uncoupled OH stretching vibration of HDO molecules in LiClO4.3H2O(s) has been calculated by quantum-mechanical ab initio and model potential methods and compared with the experimental infrared frequency from isotope-isolated HDO molecules. The effects of the nearest neighbours as well as of the crystalline environment have been investigated by the two computational techniques. In both cases, the one-dimensional potential for an anharmonic OH oscillator was constructed from point-wise energy calculations and the Schrodinger equation for the protonic motion in this potential well was solved by a variational procedure. In the ab initio calculations, vibrational potentials were constructed from RHF and MP2 type calculations of point-charge embedded ClO4-.HDO and (Li+)2.(ClO4-)2.HDO clusters using DZP and TZP basis sets. For the LiClO4.3H2O(s) crystal, the ab initio OH frequency is in close quantitative agreement with experiment when electron correlation by MP2 and the crystal field are included: 3537 cm-1 (MP2(TZP)) versus the experimental value of 3556 cm-1. Inclusion of the crystal field is essential and can in this crystal be satisfactorily represented by Ewald field-consistent point charges outside the hydrogen-bonded ClO4-...HDO cluster. In the model potential calculations, analytical intermolecular pair potential functions from the literature were used in conjunction with an experimental intramolecular potential function for the OH stretching motion. The particular intermolecular model chosen here yields an absolute OH frequency 160 cm-1 below experiment. These calculations exemplify some of the difficulties encountered when employing analytical model potentials in vibrational studies.

  • 33.
    Panchmatia, Pooja M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    GGA+U modeling of structural, electronic, and magnetic properties of iron porphyrin-type molecules2008In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 343, no 1, p. 47-60Article in journal (Refereed)
    Abstract [en]

    An ab initio computational study of various iron porphyrin-type molecules has been performed. Our ab initio calculations are based on the density functional theory (DFT) and have been conducted using the generalized gradient approximation (GGA, with PW91 & PBE versions) as well as GGA + U approach, in which an additional Hubbard-U term is added for the treatment of strong on-site 3d electron-electron interactions on Fe. We have, first, optimized the atomic distances for the porphyrin models by minimizing the total energy. Second, we benchmarked our computational approach by comparison to existing calculated results for relatively small porphyrin models obtained by the Becke-Lee-Yang-Parr (BLYP) exchange-correlation functional. We have considered several models of ligated porphyrins (Cl and NH3 ligated), as well as charged and neutral molecules, to study properties of the molecules as a function of oxidation state and local chemical environment of the Fe atom. We find that the GGA + U (with U approximate to 4 eV) approach provides a better description of the molecular electronic properties for five coordinated (Fe-III) systems than the standard GGA approach, which indicates that Coulombic electron interaction effects on the Fe are important and play an essential role, particularly for the spin moment on the molecule. Also, we proceed to a larger, more realistic Fe-porphyrin model (FeP), for which we also investigate the performance of the GGA and GGA + U functionals. The character of the electronic states involved in the chemical bonding has been analyzed with the aid of energy resolved charge densities.

  • 34. Potts, A. W.
    et al.
    Holland, D. M. P.
    Powis, I.
    Karlsson, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Trofimov, A. B.
    Bodzuk, I. L.
    A study of the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene2013In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 415, p. 84-97Article in journal (Refereed)
    Abstract [en]

    A combined experimental and theoretical investigation has been performed to study the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene. Angle resolved photoelectron spectra of meta-dichlorobenzene have been recorded using synchrotron radiation in the photon energy range from close to threshold to 100 eV. These have enabled photoelectron anisotropy parameters and branching ratios to be derived. The continuum multiple scattering approach has been employed to calculate photoionisation partial cross-sections and photoelectron angular distributions of the outer valence orbitals of meta-dichlorobenzene. A comparison between the corresponding experimental and theoretical results has demonstrated that ionisation from some of the orbitals is influenced by the Cooper minimum associated with the chlorine atom. Ionisation energies and spectral intensities evaluated with the third-order algebraic diagrammatic construction approximation for the one-particle Green's function and the outer valence Green's function approaches have allowed the features observed in the complete valence shell photoelectron spectra of meta-dichlorobenzene and meta-bromochlorobenzene to be interpreted. Many-body phenomena strongly influence ionisation from the inner valence orbitals and lead to the intensity associated with a particular orbital being redistributed amongst numerous satellites. High resolution photoelectron spectra have been recorded with HeI radiation. Vibrational structure has been observed in some of the photoelectron bands and tentative assignments have been proposed. 

  • 35. Powis, I.
    et al.
    Trofimov, A. B.
    Bodzuk, I. L.
    Holland, D. M. P.
    Potts, A. W.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    A study of the valence shell electronic structure and photoionisation dynamics of para-dichlorobenzene and para-bromochlorobenzene2013In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 415, p. 291-308Article in journal (Refereed)
    Abstract [en]

    The valence shell electronic structure and photoionisation dynamics of para-dichlorobenzene and para-bromochlorobenzene have been investigated both experimentally and theoretically. High resolution photoelectron spectra of the outer valence orbitals have been recorded with HeI radiation and the observed structure has been interpreted using calculated ionisation energies and spectral intensities. The theoretical predictions for the single-hole ionic states due to outer valence ionisation agree satisfactorily with the experimental results. Ionisation from the inner valence orbitals is strongly influenced by many-body effects and the with a particular orbital is spread amongst numerous satellites. Some of the photoelectron bands exhibit vibrational progressions and tentative assignments have been proposed. The photoionisation dynamics of the outer valence orbitals of para-dichlorobenzene have been investigated theoretically by using the continuum multiple scattering approach to calculate photoionisation partial cross-sections and photoelectron anisotropy parameters. The results show that ionisation from some of the orbitals is affected by the Cooper minimum associated with the chlorine atom. Synchrotron radiation has been used to record angle resolved photoelectron spectra of the entire valence shell, for photon energies between threshold and similar to 100 eV, and these have allowed the corresponding experimental data to be derived. A comparison between the predicted and measured anisotropy parameters confirms the influence of the Cooper minimum in those orbitals related to the chlorine lone-pairs.

  • 36.
    Roos, A. Hult
    et al.
    Univ Gothenburg, Dept Phys, Origovagen 6B, S-41296 Gothenburg, Sweden.
    Eland, J. H. D.
    Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, South Parks Rd, Oxford OX1 3QZ, England;Univ Gothenburg, Dept Phys, Origovagen 6B, S-41296 Gothenburg, Sweden.
    Koulentianos, D.
    Univ Gothenburg, Dept Phys, Origovagen 6B, S-41296 Gothenburg, Sweden.
    Squibb, R. J.
    Univ Gothenburg, Dept Phys, Origovagen 6B, S-41296 Gothenburg, Sweden.
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Feifel, R.
    Univ Gothenburg, Dept Phys, Origovagen 6B, S-41296 Gothenburg, Sweden.
    Valence double ionization electron spectra of CH3F, CH3Cl and CH3I2017In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 491, p. 42-47Article in journal (Refereed)
    Abstract [en]

    Valence double ionization electron spectra of the methyl fluoride, methyl chloride, and methyl iodide molecules have been recorded using a time-of-flight photoelectron-photoelectron coincidence technique. The spectra are interpreted by comparison with existing ionization data, Auger spectra, and theoretical calculations. The lowest double ionization energies have been found to be around 35.0 eV, 30.6 eV, and 26.67 eV for CH3F, CH3Cl and CH3I, respectively. These energies are also compared with the predictions and implications of an empirical rule for the lowest double ionization energy in molecules.

  • 37. Rudberg, E
    et al.
    Brinck, T
    Computation of Franck-Condon factors for many-atom systems: simulated photoelectron spectra of formic acid isotopologues2004In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 302, no 1-3, p. 217-228Article in journal (Refereed)
  • 38.
    Salhi-Benachenhou, Nessima
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Engels, B
    Huang, M B
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Theoretical study of the ethylene radical cation: geometry and hyperfine structure1998In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 236, no 1-3, p. 53-61Article in journal (Refereed)
    Abstract [en]

    The geometry and the hyperfine structure in the ethylene radical cation have been studied by means of a number of high-level post-SCF ab initio methods, including quadratic CI with single and double substitutions and perturbative triple corrections, QCISD(T), coupled cluster with single and double substitutions and perturbative triple corrections, CCSD(T), and individually selected multi-reference CI with B-K correction, (MRD-CI)/B-K. A value of 20.2 degrees has been computed for the torsion angle in this cation with the QCISD(T)/6-311G(d, p) method, which compares favourably with the experimentally reported angle of similar to 25 degrees. The computed potential barrier to inversion through the planar conformation, as obtained at the QCISD(T)/6-311 + + G(2df, p)//QCISD(T)/6-31 1G(d, p) level (1.24 kJ/mol), is smaller than the experimental value of similar to 3 kJ/mol, but an order of magnitude better than in previous work. The hyperfine coupling constants of the protons and of C-13 are calculated by the (MRD-CI)/B-K method with a relatively large basis set, yielding somewhat larger absolute values than the experimental couplings (-4.0 G for the protons and +6.0 G for C-13, as compared with -2.4 and +4.0 G, respectively). For both the geometrical parameters and the hyperfine couplings, the results of the present study are in considerably better agreement with experiment than previously reported theoretical results.

  • 39.
    Sjöqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
    Goscinski, Osvaldo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
    The molecular Aharonov-Bohm effect for bound states beyond the adiabatic approximation1994In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 186, no 1, p. 17-26Article in journal (Refereed)
    Abstract [en]

    The linear Exe Jahn-Teller model with an “extrinsic” Aharonov-Bohm solenoid of strength α, previously studied by Mead at the adiabatic level, is generalized to the vicbronic case. Energies and eigenfunctions of the full vibronic Hamiltonian are calculated using eigenfunctions of a two-dimensional harmonic oscillator with the solenoid at the origin. Oscillating spin denstities and concomitant Ham's reduction factors are evaluated. The neglect of the diagonal vector potentials is equivalent to α= 1/2 and, in this case, the reduction factors vanish for vibronic angular momentum j = 1/2. The symmetries of the model are studied by partitioning technique. In the adiabatic regime, vibronic spectra with α=0 and 1/2 are compared to adiabatic calculations showing that the neglect of the diagonal vector potentials influences the spectra more than the adiabatic approximation. Finally, with α=1/2, degeneracies in the spectra show up at some vibronic coupling strengths, indicating a hidden dynamical symmetry.

  • 40.
    Spinlove, K. E.
    et al.
    Univ Birmingham, Sch Chem, Birmingham B15 2TT, W Midlands, England.;Imperial Coll London, Dept Chem, South Kensington SW7 2AZ, England..
    Vacher, Morgane
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Imperial Coll London, Dept Chem, South Kensington SW7 2AZ, England..
    Bearpark, M.
    Imperial Coll London, Dept Chem, South Kensington SW7 2AZ, England..
    Robb, M. A.
    Imperial Coll London, Dept Chem, South Kensington SW7 2AZ, England..
    Worth, G. A.
    Univ Birmingham, Sch Chem, Birmingham B15 2TT, W Midlands, England.;UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England..
    Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules2017In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 482, p. 52-63Article in journal (Refereed)
    Abstract [en]

    Recent work, particularly by Cederbaum and co-workers, has identified the phenomenon of charge migration, whereby charge flow occurs over a static molecular framework after the creation of an electronic wavepacket. In a real molecule, this charge migration competes with charge transfer, whereby the nuclear motion also results in the re-distribution of charge. To study this competition, quantum dynamics simulations need to be performed. To break the exponential scaling of standard grid-based algorithms, approximate methods need to be developed that are efficient yet able to follow the coupled electronic-nuclear motion of these systems. Using a simple model Hamiltonian based on the ionisation of the allene molecule, the performance of different methods based on Gaussian Wavepackets is demonstrated.

  • 41.
    Timneanu, Nicusor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Hajdu, Janos
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    van der Spoel, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Auger electron cascades in water and ice2004In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 299, p. 277-283Article in journal (Refereed)
    Abstract [en]

    Secondary electron cascades can induce significant ionisation in condensed matter due to electron–atom collisions. This is of interest in the context of diffraction and imaging using X-rays, where radiation damage is the main limiting factor for achieving high resolution data. Here we present new results on electron-induced damage on liquid water and ice, from the simulation of Auger electron cascades. We have compared our theoretical estimations to the available experimental data on elastic and inelastic electron–molecule interactions for water and found the theoretical results for elastic cross-sections to be in very good agreement with experiment. As a result of the cascade we find that the average number of secondary electrons after 100 fs in ice is about 25, slightly higher than in water, where it is about 20. The difference in damage between ice and water is discussed in the context of sample handling for biomolecular systems.

  • 42.
    Westermark, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Henningsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Södergren, Sven
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Determination of the electronic density of states at a nanostructured TiO2/Ru-dye/electrolyte interface by means of photoelectron spectroscopy2002In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 285, no 1, p. 157-165Article in journal (Refereed)
    Abstract [en]

    In this work, photoelectron spectroscopy is used to measure the electronic density of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and in this study a plain TiO2 film as well as a dye-sensitized film were examined. Further, to simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the density of states in the band gap region for an electrochemically prepared TiO2 film inserted with Li+ ions was measured. From the experimental findings we discuss the distribution and chemical nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4-dicarboxy-2,2-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge.

  • 43. WOJCIK, MAREK J
    et al.
    HERMANSSON, KERSTI
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    LINDGREN, JAN
    OJAMAE, LARS
    THEORETICAL SIMULATION OF OH AND OD STRETCHING BANDS OF ISOTOPICALLY DILUTED HDO MOLECULES IN AQUEOUS-SOLUTION1993In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 171, no 1-2, p. 189-201Article in journal (Refereed)
    Abstract [en]

    Uncoupled OH and OD stretching bands of HDO molecules have been calculated for an ionic aqueous solution, based on the trajectories from a classical statistical-mechanical computer simulation and subsequent quantum-mechanical calculations of the vibrational energy levels. Each V(r(OH)) potential function has been constructed as a sum of intra- and intermolecular energies, where different intermolecular water-water potential functions from the literature (MCY, TIPS2, RWK2 and CF2) have been tested in conjunction with the experimentally derived HMS intramolecular potential. In this way, vibrational densities-of-states as well as infrared absorption bands have been calculated for HDO molecules in the bulk and in the ionic hydration shells (Li+, HCOO-). Calculated frequencies and band widths for the TIPS2 and MCY potentials are fairly close to experimental values. The calculated OH shift between the gas and liquid water phases is - 303 cm-1 with the TIPS2 potential, as compared to the experimental value of - 307 cm-1. The MCY potential gives - 260 cm-1, while RWK2 as well as the CF2 potentials give rise to a non-negligible number of spurious frequencies. Water molecules in the first hydration shell of Li+ exhibit only slightly lower stretching frequencies than bulk water. The frequencies of the OH and OD groups of HDO molecules bonded to the formate oxygen atoms are lower than in bulk water, while the frequency of the OH/OD group pointing away from the formate ion is higher compared to bulk water.

  • 44.
    Zagorodskikh, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Zhaunerchyk, Vitali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Mucke, Melaine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Eland, John H. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden.;Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, Oxford OX1 3QZ, England..
    Squibb, R. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Karlsson, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Linusson, P.
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Feifel, Raimund
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Single-photon double and triple ionization of acetaldehyde (ethanal) studied by multi-electron coincidence spectroscopy2015In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 463, p. 159-168Article in journal (Refereed)
    Abstract [en]

    Single-photon multiple ionization processes of acetaldehyde (ethanal) have been experimentally investigated by utilizing a multi-particle coincidence technique based on the time-of-flight magnetic bottle principle, in combination with either a synchrotron radiation source or a pulsed helium discharge lamp. The processes investigated include double and triple ionization in the valence region as well as single and double Auger decay of core-ionized acetaldehyde. The latter are studied site-selectively for chemically different carbon core vacancies, scrutinizing early theoretical predictions specifically made for the case of acetaldehyde. Moreover, Auger processes in shake-up and core-valence ionized states are investigated. In the cases where the processes involve simultaneous emission of two electrons, the distributions of the energy sharing are presented, emphasizing either the knock-out or shake-off mechanism.

1 - 44 of 44
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