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BETA
Karlsson, Leif
Alternative names
Publications (10 of 43) Show all publications
Holland, D. M., Powis, I., Trofimov, A. B., Menzies, R. C., Potts, A. W., Karlsson, L., . . . Schirmer, J. (2017). An experimental and theoretical study of the valence shell photoelectron spectra of 2-chloropyridine and 3-chloropyridine. Journal of Chemical Physics, 147(16), Article ID 164307.
Open this publication in new window or tab >>An experimental and theoretical study of the valence shell photoelectron spectra of 2-chloropyridine and 3-chloropyridine
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, no 16, article id 164307Article in journal (Refereed) Published
Abstract [en]

The valence shell photoelectron spectra of 2-chloropyridine and 3-chloropyridine have been studied both experimentally and theoretically. Synchrotron radiation has been employed to record angle resolved photoelectron spectra in the photon energy range 20-100 eV, and these have enabled anisotropy parameters and branching ratios to be derived. The experimental results have been compared with theoretical predictions obtained using the continuum multiple scattering X alpha approach. This comparison shows that the anisotropy parameter associated with the nominally chlorine lone-pair orbital lying in the molecular plane is strongly affected by the atomic Cooper minimum. In contrast, the photoionization dynamics of the second lone-pair orbital, orientated perpendicular to the molecular plane, seem relatively unaffected by this atomic phenomenon. The outer valence ionization has been studied theoretically using the third-order algebraic-diagrammatic construction (ADC(3)) approximation scheme for the one-particle Green's function, the outer valence Green's function method, and the equation-of-motion (EOM) coupled cluster (CC) theory at the level of the EOM-IP-CCSD and EOM-EE-CC3 models. The convergence of the results to the complete basis set limit has been investigated. The ADC(3) method has been employed to compute the complete valence shell ionization spectra of 2-chloropyridine and 3-chloropyridine. The relaxation mechanism for ionization of the nitrogen sigma-type lone-pair orbital (sigma(N) (LP)) has been found to be different to that for the corresponding chlorine lone-pair (sigma(Cl) (LP)). For the sigma(N) (LP) orbital, pi-pi* excitations play the main role in the screening of the lone-pair hole. In contrast, excitations localized at the chlorine site involving the chlorine pi(Cl) (LP) lone-pair and the Cl 4p Rydberg orbital are the most important for the sigma(Cl) (LP) orbital. The calculated photoelectron spectra have allowed assignments to be proposed for most of the structure observed in the experimental spectra. The theoretical work also highlights the formation of satellite states, due to the breakdown of the single particle model of ionization, in the inner valence region.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-341369 (URN)10.1063/1.4999433 (DOI)000414177600063 ()29096444 (PubMedID)
Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-02-08Bibliographically approved
Trofimov, A. B., Holland, D. M., Powis, I., Menzies, R. C., Potts, A. W., Karlsson, L., . . . Schirmer, J. (2017). Ionization of pyridine: Interplay of orbital relaxation and electron correlation. Journal of Chemical Physics, 146(24), Article ID 244307.
Open this publication in new window or tab >>Ionization of pyridine: Interplay of orbital relaxation and electron correlation
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24, article id 244307Article in journal (Refereed) Published
Abstract [en]

The valence shell ionization spectrum of pyridine was studied using the third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green's function and the outer-valence Green's function method. The results were used to interpret angle resolved photoelectron spectra recorded with synchrotron radiation in the photon energy range of 17-120 eV. The lowest four states of the pyridine radical cation, namely, (2)A(2)(1a(2)(-1)), (2)A(1)(7a(1)(-1)), B-2(1)(2b(1)(-1)), and B-2(2)(5b(2)(-1)), were studied in detail using various high-level electronic structure calculation methods. The vertical ionization energies were established using the equation-of-motion coupled-cluster approach with single, double, and triple excitations (EOM-IP-CCSDT) and the complete basis set extrapolation technique. Further interpretation of the electronic structure results was accomplished using Dyson orbitals, electron density difference plots, and a second-order perturbation theory treatment for the relaxation energy. Strong orbital relaxation and electron correlation effects were shown to accompany ionization of the 7a1 orbital, which formally represents the nonbonding sigma-type nitrogen lone-pair (n sigma) orbital. The theoretical work establishes the important roles of the pi-system (pi-pi* excitations) in the screening of the n sigma-hole and of the relaxation of the molecular orbitals in the formation of the 7a(1)(n sigma)(-1) state. Equilibrium geometric parameters were computed using the MP2 (second-order Moller-Plesset perturbation theory) and CCSD methods, and the harmonic vibrational frequencies were obtained at the MP2 level of theory for the lowest three cation states. The results were used to estimate the adiabatic 0-0 ionization energies, which were then compared to the available experimental and theoretical data. Photoelectron anisotropy parameters and photoionization partial cross sections, derived from the experimental spectra, were compared to predictions obtained with the continuum multiple scattering approach.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-330724 (URN)10.1063/1.4986405 (DOI)000404302600022 ()28668050 (PubMedID)
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2017-10-10Bibliographically approved
Roos, A. H., Eland, J. H., Koulentianos, D., Squibb, R. J., Karlsson, L. & Feifel, R. (2017). Valence double ionization electron spectra of CH3F, CH3Cl and CH3I. Chemical Physics, 491, 42-47
Open this publication in new window or tab >>Valence double ionization electron spectra of CH3F, CH3Cl and CH3I
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2017 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 491, p. 42-47Article in journal (Refereed) Published
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.

National Category
Atom and Molecular Physics and Optics Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-361064 (URN)10.1016/j.chemphys.2017.04.002 (DOI)000404317700005 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, FP7, Seventh Framework Programme, 312284
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-09-21Bibliographically approved
Holland, D. M., Powis, I., Trofimov, A. B., Bodzuk, I. L., Soshnikov, D. Y., Potts, A. W. & Karlsson, L. (2015). A study of the valence shell electronic structure and photoionisation dynamics of ortho-dichlorobenzene, ortho-bromochlorobenzene and trichlorobenzene. Chemical Physics, 448, 61-75
Open this publication in new window or tab >>A study of the valence shell electronic structure and photoionisation dynamics of ortho-dichlorobenzene, ortho-bromochlorobenzene and trichlorobenzene
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2015 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 448, p. 61-75Article in journal (Refereed) Published
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.

Keywords
Valence shell electronic structure, Photoionisation dynamics, Franck-Condon simulations, Synchrotron radiation, Photoelectron angular distributions, Cooper minimum
National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-251528 (URN)10.1016/j.chemphys.2014.11.025 (DOI)000350747000008 ()
Available from: 2015-04-22 Created: 2015-04-20 Last updated: 2017-12-04Bibliographically approved
Zagorodskikh, S., Zhaunerchyk, V., Mucke, M., Eland, J. H. D., Squibb, R. J., Karlsson, L., . . . Feifel, R. (2015). Single-photon double and triple ionization of acetaldehyde (ethanal) studied by multi-electron coincidence spectroscopy. Chemical Physics, 463, 159-168
Open this publication in new window or tab >>Single-photon double and triple ionization of acetaldehyde (ethanal) studied by multi-electron coincidence spectroscopy
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2015 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 463, p. 159-168Article in journal (Refereed) Published
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.

Keywords
Acetaldehyde, Double ionization, Triple ionisation, Site-specific Auger decay
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-270927 (URN)10.1016/j.chemphys.2015.10.006 (DOI)000365582100021 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, European Research Council, R II 3-CT-2004-506008
Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2017-12-01Bibliographically approved
Tibbelin, J., Wallner, A., Emanuelsson, R., Heijkenskjöld, F., Rosenberg, M., Yamazaki, K., . . . Ottosson, H. (2014). 1,4-Disilacyclohexa-2,5-diene: a molecular building block that allows for remarkably strong neutral cyclic cross-hyperconjugation. Chemical Science, 5(1), 360-371
Open this publication in new window or tab >>1,4-Disilacyclohexa-2,5-diene: a molecular building block that allows for remarkably strong neutral cyclic cross-hyperconjugation
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2014 (English)In: Chemical Science, ISSN 2041-6520, Vol. 5, no 1, p. 360-371Article in journal (Refereed) Published
Abstract [en]

2,3,5,6-Tetraethyl-1,4-disilacyclohexa-2,5-dienes with either four chloro (1a), methyl (1b), or trimethylsilyl (TMS) (1c) substituents at the two silicon atoms were examined in an effort to design rigid compounds with strong neutral cross-hyperconjugation between pi- and sigma-bonded molecular segments arranged into a cycle. Remarkable variations in the lowest electronic excitation energies, lowest ionization energies, and the first oxidation potentials were observed upon change of substituents, as determined by gas phase ultraviolet (UV) absorption spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and cyclic voltammetry. A particularly strong neutral cyclic cross-hyperconjugation was observed in 1c. Its lowest electron binding energy (7.1 eV) is distinctly different from that of 1b (8.5 eV). Molecular orbital analysis reveals a stronger interaction between filled pi(C=C) and pi(SiR2) group orbitals in 1c than in 1a and 1b. The energy shift in the highest occupied molecular orbital is also reflected in the first oxidation potentials as observed in the cyclic voltammograms of the respective compounds (1.47, 0.88, and 0.46 V for 1a, 1b and 1c, respectively). Furthermore, 1,4-disilacyclohexadiene 1c absorbs strongly at 273 nm (4.55 eV), whereas 1a and 1b have no symmetry allowed excitations above 215 nm (below 5.77 eV). Thus, suitably substituted 1,4-disilacyclohexa-2,5-dienes could represent novel building blocks for the design of larger cross-hyperconjugated molecules as alternatives to traditional purely cross-p-conjugated analogues, and could allow for design of molecules with properties that are not accessible to those that are exclusively pi-conjugated.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-213891 (URN)10.1039/c3sc52389f (DOI)000327601600045 ()
Available from: 2014-01-06 Created: 2014-01-05 Last updated: 2016-03-08Bibliographically approved
Hedin, L., Tashiro, M., Linusson, P., Eland, J. H., Ehara, M., Ueda, K., . . . Feifel, R. (2014). N1s and O1s double ionization of the NO and N2O molecules. Journal of Chemical Physics, 140(4), 044309
Open this publication in new window or tab >>N1s and O1s double ionization of the NO and N2O molecules
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2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 4, p. 044309-Article in journal (Refereed) Published
Abstract [en]

Single-site N1s and O1s double core ionisation of the NO and N2O molecules has been studied using a magnetic bottle many-electron coincidence time-of-flight spectrometer at photon energies of 1100 eV and 1300 eV. The double core hole energies obtained for NO are 904.8 eV (N1s(-2)) and 1179.4 eV (O1s(-2)). The corresponding energies obtained for N2O are 896.9 eV (terminal N1s(-2)), 906.5 eV (central N1s(-2)), and 1174.1 eV (O1s(-2)). The ratio between the double and single ionisation energies are in all cases close or equal to 2.20. Large chemical shifts are observed in some cases which suggest that reorganisation of the electrons upon the double ionization is significant. Delta-self-consistent field and complete active space self-consistent field (CASSCF) calculations were performed for both molecules and they are in good agreement with these results. Auger spectra of N2O, associated with the decay of the terminal and central N1s(-2) as well as with the O1s(-2) dicationic states, were extracted showing the two electrons emitted as a result of filling the double core holes. The spectra, which are interpreted using CASSCF and complete active space configuration interaction calculations, show atomic-like character. The cross section ratio between double and single core hole creation was estimated as 1.6 x 10(-3) for nitrogen at 1100 eV and as 1.3 x 10(-3) for oxygen at 1300 eV. (C) 2014 AIP Publishing LLC.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-220812 (URN)10.1063/1.4853655 (DOI)000331211700035 ()
Available from: 2014-03-21 Created: 2014-03-20 Last updated: 2017-12-05Bibliographically approved
Hedin, L., Tashiro, M., Linusson, P., Eland, J. H. D., Ehara, M., Ueda, K., . . . Feifel, R. (2014). Single site double core level ionisation of OCS. Chemical Physics, 439, 111-116
Open this publication in new window or tab >>Single site double core level ionisation of OCS
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2014 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 439, p. 111-116Article in journal (Refereed) Published
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. 

Keywords
Double core hole states, Electron spectra, Magnetic bottle multi-electron coincidence spectrometer, Cross section ratios
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-229702 (URN)10.1016/j.chemphys.2014.05.012 (DOI)000338705600015 ()
Available from: 2014-08-12 Created: 2014-08-12 Last updated: 2017-12-05Bibliographically approved
Potts, A. W., Holland, D. M., Powis, I., Karlsson, L., Trofimov, A. B. & Bodzuk, I. L. (2013). A study of the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene. Chemical Physics, 415, 84-97
Open this publication in new window or tab >>A study of the valence shell electronic structure and photoionisation dynamics of meta-dichlorobenzene and meta-bromochlorobenzene
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2013 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 415, p. 84-97Article in journal (Refereed) Published
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. 

Keywords
Photoelectron spectrum, Electronic structure, Photoionisation dynamics, Meta-dichlorobenzene, Meta-bromochlorobenzene
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-200105 (URN)10.1016/j.chemphys.2012.12.031 (DOI)000317277300013 ()
Available from: 2013-05-22 Created: 2013-05-20 Last updated: 2017-12-06Bibliographically approved
Powis, I., Trofimov, A. B., Bodzuk, I. L., Holland, D. M., Potts, A. W. & Karlsson, L. (2013). A study of the valence shell electronic structure and photoionisation dynamics of para-dichlorobenzene and para-bromochlorobenzene. Chemical Physics, 415, 291-308
Open this publication in new window or tab >>A study of the valence shell electronic structure and photoionisation dynamics of para-dichlorobenzene and para-bromochlorobenzene
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2013 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 415, p. 291-308Article in journal (Refereed) Published
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.

Keywords
Molecular photoionisation dynamics, Valence shell electronic structure, Halogen atom Cooper minimum, Many-body effects, Para-dichlorobenzene, Para-bromochlorobenzene
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-200106 (URN)10.1016/j.chemphys.2012.09.026 (DOI)000317277300041 ()
Available from: 2013-05-22 Created: 2013-05-20 Last updated: 2017-12-06Bibliographically approved
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