Vibrational State Dependence of the Photoelectron Angular Asymmetry Parameter caused by Vibronic Coupling

Domcke, Wolfgang

doi:10.1088/0031-8949/19/1/002

Cited by 33 publications

(6 citation statements)

References 26 publications

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“…[3][4][5] Less common have been theoretically backed investigations of explicit vibrational influences exerted on the photoelectron angular distributions (PADs). The influence of full Herzberg-Teller type vibronic interaction has been discussed [6] in this context, but more typically approaches based upon treating the parametric dependence of the electronic matrix element upon nuclear geometry have provided understanding. Such investigations have mainly addressed the localized K-edge ionization of diatomic [7][8][9][10][11] and triatomic [12,13] molecules in the vicinity of shape resonances.…”

Section: Introductionmentioning

confidence: 99%

Identifying and Understanding Strong Vibronic Interaction Effects Observed in the Asymmetry of Chiral Molecule Photoelectron Angular Distributions

et al. 2017

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Ivan (2017) Identifying and understanding strong vibronic interaction effects observed in the asymmetry of chiral molecule photoelectron angular distributions. ChemPhysChem, 18 (5 A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractElectron-ion coincidence imaging is used to study chiral asymmetry in the angular distribution of electrons emitted from randomly-oriented enantiomers of two molecules, methyloxirane and trifluoromethyloxirane, upon ionization by circularly polarized VUV synchrotron radiation. Vibrationally-resolved photoelectron circular dichroism (PECD) measurements of the outermost orbital ionization reveal unanticipated large fluctuations in the magnitude of the forward-backward electron scattering asymmetry, including even a complete reversal of direction. Identification and assignment of the vibrational excitations is supported by Franck-Condon simulations of the photoelectron spectra. A previously proposed quasi-diatomic model for PECD is developed and extended to treat polyatomic systems. The parametric dependence of the electronic dipole matrix elements on nuclear geometry is evaluated in the adiabatic approximation, and provokes vibrational level dependent shifts in amplitude and phase, to which the chiral photoelectron angular distributions are especially sensitive. It is shown that single quantum excitation of those vibrational modes which experience only a relatively small displacement of the ion equilibrium geometry along the normal coordinate, and which are then only weakly excited in the Franck-Condon limit, can be accompanied by big shifts in scattering phase; hence the observed big fluctuations in PECD asymmetry for such modes.

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Section: Introductionmentioning

confidence: 99%

Identifying and Understanding Strong Vibronic Interaction Effects Observed in the Asymmetry of Chiral Molecule Photoelectron Angular Distributions

et al. 2017

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“…Theoretically, it can be expected that when the dynamics are formed by two interacting states, the observed asymmetry will be determined by the leading term in the state expansion. 83 This has been observed, for example, in the photoelectron band system due to the A 2 B2, B 2 A1, and C 2 A2 states of cis-dichloroethene 76 with the vibronic interaction confirmed by ab initio calculation. 77 The structure observed in the photoelectron band of imidazole around 14 eV can be qualitatively reproduced by Franck-Condon simulation for the 14a ionization (albeit with, again, a surprisingly large rescaling of the calculated harmonic frequencies) but this rather contradicts the -parameter measurement for this band which has been interpreted as indicating a significant -type character, putatively from the 1a satellite.…”

Section: Please Cite This Articlementioning

confidence: 77%

Valence shell photoelectron angular distributions and vibrationally resolved spectra of imidazole: A combined experimental–theoretical study

Patanen

Abid

Pratt

et al. 2021

The Journal of Chemical Physics

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Linearly polarized synchrotron radiation has been used to record polarization dependent valence shell photoelectron spectra of imidazole in the photon energy range 21 -100 eV. These have allowed the photoelectron angular distributions, as characterized by the anisotropy parameter β, and the electronic state intensity branching ratios to be determined.Complementing these experimental data, theoretical photoionization partial cross sections and β-parameters have been calculated for the outer valence shell orbitals. The assignment of the structure appearing in the experimental photoelectron spectra has been guided by vertical ionization energies and spectral intensities calculated by various theoretical methods which incorporate electron correlation and orbital relaxation. Strong orbital relaxation effects have been found for the 15aʹ, nitrogen lone-pair orbital. The calculations also predict that configuration mixing leads to the formation of several low-lying satellite states. The vibrational structure associated with ionization out of a particular orbital has been simulated within the Franck-Condon model, using harmonic vibrational modes. The adiabatic approximation appears to be valid for the X 2 Aʺ state, with the β-parameter for this state being independent of the level of vibrational excitation. However, for all the other outer valence ionic states, a disparity occurs between the observed and the simulated vibrational structure, and the measured β-parameters are at variance with the behaviour expected at the level of the Franck-Condon approximation. These inconsistencies suggest that the excited electronic states may be interacting vibronically such that the nuclear dynamics occur over coupled potential energy surfaces.

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“…25 This dependence on the vibrational states is more evident when higher excited vibrational quantum numbers of the normal modes are involved, i.e., the highest IE part of the region between a and b peaks and around the c band. 25 This dependence on the vibrational states is more evident when higher excited vibrational quantum numbers of the normal modes are involved, i.e., the highest IE part of the region between a and b peaks and around the c band.…”

Section: Resultsmentioning

confidence: 99%

Vibrational state dependence of β and D asymmetry parameters: The case of the highest occupied molecular orbital photoelectron spectrum of methyl-oxirane

Contini

Zema

Turchini

et al. 2007

The Journal of Chemical Physics

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The beta angular asymmetry and D dichroic asymmetry parameters of the methyl-oxirane highest occupied molecular orbital (HOMO) band have been experimentally investigated with vibrational resolution using synchrotron radiation. A theoretical calculation of the Franck-Condon factors between vibrational ground state and different ionic vibrational states, in the Born-Oppenheimer harmonic approximation, has been performed in order to gain information on the vibrational states mainly involved in the HOMO photoelectron band. The general good agreement between theoretical and experimental results allows a reliable assignment of the major features. The experimental determination of beta and D shows their dependence on the different final vibrational states. This paper reports, for the first time, experimental evidence of the dependence of the dichroic D parameter on the vibrational excitation of the ion.

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Vibrational State Dependence of the Photoelectron Angular Asymmetry Parameter caused by Vibronic Coupling

Cited by 33 publications

References 26 publications

Identifying and Understanding Strong Vibronic Interaction Effects Observed in the Asymmetry of Chiral Molecule Photoelectron Angular Distributions

Identifying and Understanding Strong Vibronic Interaction Effects Observed in the Asymmetry of Chiral Molecule Photoelectron Angular Distributions

Valence shell photoelectron angular distributions and vibrationally resolved spectra of imidazole: A combined experimental–theoretical study

Vibrational state dependence of β and D asymmetry parameters: The case of the highest occupied molecular orbital photoelectron spectrum of methyl-oxirane

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