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Feifel, Raimund
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Publications (10 of 55) Show all publications
Valiev, R. R., Eland, J. H. D., Feifel, R. & Ågren, H. (2017). Optimization of core-valence states of molecules. Molecular Physics, 115(1-2), 252-259
Open this publication in new window or tab >>Optimization of core-valence states of molecules
2017 (English)In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 115, no 1-2, p. 252-259Article in journal (Refereed) Published
Abstract [en]

Core-valence double-electron ionisation spectra of a few small molecules - arbon monoxide, ammonia, methyl fluoride and thiophene - are presented and analysed using the self-consistent field algorithm introduced by Hans Jorgen Jensen 30 years ago. It confirms the utility of this algorithm, frequently employed to obtain stable and sharp convergence of wave functions for the benefit of calculations of a great variety of molecular properties, thus also for optimisation of core-valence states and for the interpretation of the corresponding spectra. [GRAPHICS]

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2017
Keywords
Core-valence states, X-ray spectroscopy, double-electron ionisation spectra, ammonia, thiophene
National Category
Atom and Molecular Physics and Optics Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-319775 (URN)10.1080/00268976.2016.1266054 (DOI)000396794700020 ()
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish Research CouncilEU, European Research Council, 312284
Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2017-11-29Bibliographically 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
Eland, J. H. D., Zagorodskikh, S., Squibb, R. J., Mucke, M., Sorensen, S. L. & Feifel, R. (2014). Carbon dioxide ion dissociations after inner shell excitation and ionization: The origin of site-specific effects. Journal of Chemical Physics, 140(18), 184305
Open this publication in new window or tab >>Carbon dioxide ion dissociations after inner shell excitation and ionization: The origin of site-specific effects
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2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 18, p. 184305-Article in journal (Refereed) Published
Abstract [en]

Multi-coincidence experiments with detection of both electrons and ions from decay of core-excited and core-ionized states of CO2 confirm that O-2(+) is formed specifically in Auger decay from the C1s-pi* and O1s-pi* resonances. Molecular rearrangement occurs by bending in the resonant states, and O-2(+) is produced by both single and double Auger decay. It is suggested that electron capture by C+ after partial dissociation in the doubly ionized core of excited CO2+, formed by shake-up in spectator resonant Auger decay, accounts for high kinetic energy and high internal energy in some C + O-2(+) fragments.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-228478 (URN)10.1063/1.4872218 (DOI)000336782700069 ()
Available from: 2014-07-15 Created: 2014-07-15 Last updated: 2017-12-05Bibliographically approved
McFarland, B., Berrah, N., Bostedt, C., Bozek, J., Bucksbaum, P., Castagna, J., . . . Gühr, M. (2014). Experimental strategies for optical pump - soft x-ray probe experiments at the LCLS. Paper presented at ICPEAC 2013. Journal of Physics: Conference Series, 488, 012015
Open this publication in new window or tab >>Experimental strategies for optical pump - soft x-ray probe experiments at the LCLS
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2014 (English)In: Journal of Physics: Conference Series, Vol. 488, p. 012015-Article in journal (Refereed) Published
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-240740 (URN)10.1088/1742-6596/488/1/012015 (DOI)
Conference
ICPEAC 2013
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2016-03-08Bibliographically approved
Zitnik, M., Mihelič, A., Bučar, K., Kavčič, M., Rubensson, J.-E., Svanqvist, M., . . . Callegari, C. (2014). High resolution multiphoton spectroscopy by a tunable free-electron-laser light. Physical Review Letters, 113(19), 193201
Open this publication in new window or tab >>High resolution multiphoton spectroscopy by a tunable free-electron-laser light
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2014 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 113, no 19, p. 193201-Article in journal (Refereed) Published
Abstract [en]

Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic and molecular species. Using the seeded free electron laser FERMI and a novel detection scheme, we have revealed the two-photon excitation spectra of dipole-forbidden doubly excited states in helium. The spectral profiles of the lowest (-1,0)^{+1} ^{1}S^{e} and (0,1)^{0} ^{1}D^{e} resonances display energy shifts in the meV range that depend on the pulse intensity. The results are explained by an effective two-level model based on calculated Rabi frequencies and decay rates.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-237722 (URN)10.1103/PhysRevLett.113.193201 (DOI)000345358100006 ()25415905 (PubMedID)
Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2017-12-05Bibliographically approved
Schalk, O., Schuurman, M. S., Wu, G., Lang, P., Mucke, M., Feifel, R. & Stolow, A. (2014). Internal Conversion versus Intersystem Crossing: What Drives the Gas Phase Dynamics of Cyclic alpha,beta-Enones?. Journal of Physical Chemistry A, 118(12), 2279-2287
Open this publication in new window or tab >>Internal Conversion versus Intersystem Crossing: What Drives the Gas Phase Dynamics of Cyclic alpha,beta-Enones?
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2014 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 12, p. 2279-2287Article in journal (Refereed) Published
Abstract [en]

We investigate the competition between intersystem crossing (ISC) and internal conversion (IC) as nonradiative relaxation pathways in cyclic alpha,beta-unsaturated enones following excitation to their lowest lying (1)pi pi* state, by means of time-resolved photoelectron spectroscopy and ab initio computation. Upon excitation, the (1)pi pi* state of 2-cyclopentenone decays to the lowest lying (1)pi pi* state within 120 +/- 20 fs. Within 1.2 +/- 0.2 ps, the molecule subsequently decays to the triplet manifold and the singlet ground state, with quantum yields of 0.35 and 0.65, respectively. The corresponding dynamics in modified derivatives, obtained by selective methylation, show a decrease in both IC and ISC rates, with the quantum yields of ISC varying between 0.35 and 0.08. The rapid rates of ISC are explained by a large spin orbit coupling of 45-60 cm(-1) over an extended region of near degeneracy between the singlet and triplet state. Furthermore, the rate of IC is depressed by the existence of a well-defined minimum on the (1)n pi* potential energy surface. The nonadiabatic pathways evinced by the present results highlight the fact that these molecular systems conceptually represent "intermediate cases" between ultrafast dynamics mediated by vibrational motions at conical intersections versus those by statistical decay mechanisms.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-224358 (URN)10.1021/jp4124937 (DOI)000333578100012 ()
Available from: 2014-05-12 Created: 2014-05-09 Last updated: 2017-12-05Bibliographically 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
Salen, P., Kaminska, M., Squibb, R. J., Richter, R., Alagia, M., Stranges, S., . . . Zhaunerchyk, V. (2014). Selectivity in fragmentation of N-methylacetamide after resonant K-shell excitation. Physical Chemistry, Chemical Physics - PCCP, 16(29), 15231-15240
Open this publication in new window or tab >>Selectivity in fragmentation of N-methylacetamide after resonant K-shell excitation
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2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 29, p. 15231-15240Article in journal (Refereed) Published
Abstract [en]

The fragmentation pattern of the peptide model system, N-methylacetamide, is investigated using ion time-of-flight (TOF) spectroscopy after resonant K-shell excitation. Corresponding near-edge X-ray absorption fine structure (NEXAFS) spectra recorded at high resolution at the C1s, N1s and O1s edges are presented. Analysis of the ion TOF data reveals a multitude of fragmentation channels and dissociation pathways. Comparison between the excitation of six different resonances in the vicinity of the C1s, N1s and O1s edges suggests evidence for site-selective bond breaking. In particular the breaking of the peptide bond and the N-C-alpha bond show a clear correlation with resonant excitation at the N1s edge. Also, stronger tendencies towards site-selective bond breaking are found for the generation of single ions compared with ion pairs. Analysis of angular distributions of ions from breakage of the peptide bond yields a fragmentation time of <400 fs.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-230538 (URN)10.1039/c4cp01067a (DOI)000339173700022 ()
Available from: 2014-08-26 Created: 2014-08-26 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
Zhaunerchyk, V., Frasinski, L. J., Eland, J. H. D. & Feifel, R. (2014). Theory and simulations of covariance mapping in multiple dimensions for data analysis in high-event-rate experiments. Physical Review A. Atomic, Molecular, and Optical Physics, 89(5), 053418
Open this publication in new window or tab >>Theory and simulations of covariance mapping in multiple dimensions for data analysis in high-event-rate experiments
2014 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 89, no 5, p. 053418-Article in journal (Refereed) Published
Abstract [en]

Multidimensional covariance analysis and its validity for correlation of processes leading to multiple products are investigated from a theoretical point of view. The need to correct for false correlations induced by experimental parameters which fluctuate from shot to shot, such as the intensity of self-amplified spontaneous emission x-ray free-electron laser pulses, is emphasized. Threefold covariance analysis based on simple extension of the two-variable formulation is shown to be valid for variables exhibiting Poisson statistics. In this case, false correlations arising from fluctuations in an unstable experimental parameter that scale linearly with signals can be eliminated by threefold partial covariance analysis, as defined here. Fourfold covariance based on the same simple extension is found to be invalid in general. Where fluctuations in an unstable parameter induce nonlinear signal variations, a technique of contingent covariance analysis is proposed here to suppress false correlations. In this paper we also show a method to eliminate false correlations associated with fluctuations of several unstable experimental parameters.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-228022 (URN)10.1103/PhysRevA.89.053418 (DOI)000336906800008 ()
Available from: 2014-07-02 Created: 2014-07-02 Last updated: 2017-12-05Bibliographically approved
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