Spin–orbit effects, electronic decay and breakdown phenomena in the photoelectron spectra of iodomethane

Pernpointner, Markus; Zobel, J. Patrick; Faßhauer, Elke; Sil, A. N.

doi:10.1016/j.chemphys.2012.08.015

Cited by 11 publications

(12 citation statements)

References 61 publications

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“…The 1a 1 and 2a 1 valence orbitals may be regarded as a σ/σ * pair formed by the interacting I 5s and C 2s/2p z atomic orbitals, and the 3a 1 (HOMO-1) orbital may be characterized as a C-I σ-bonding orbital. These characterizations of the valence shell molecular orbitals in terms of the atomic contributions are in accord with those reported by Pernpointner et al 65 Plots of the valence orbitals are available in the supplementary material. These predictions rationalize the Table III.…”

Section: N 45 O 23 and M 45 N 45 V Transitionssupporting

confidence: 86%

Auger electron angular distributions following excitation or ionization of the I 3d level in methyl iodide

Forbes

Fanis

Bomme

et al. 2018

The Journal of Chemical Physics

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Auger electron spectra following excitation or ionization of the I 3d level in CH3I have been recorded with horizontally or vertically plane polarized synchrotron radiation. These spectra have enabled the Auger electron angular distributions, as characterized by the β parameter, to be determined. The I 3d photoionization partial cross section of CH3I has been calculated with the continuum multiple scattering approach, and the results show that in the photon energy range over which Auger spectra were measured, the I 3d cross section exhibits an atomic-like behavior and is dominated by transitions into the εf continuum channel. In this limit, the theoretical value of the alignment parameter (A20) characterizing the core ionized state in an atom becomes constant, independent of photon energy. This theoretical value has been used to obtain the Auger electron intrinsic anisotropy parameters (α2) from the β parameters extracted from our normal (non-resonant) molecular Auger spectra. The resulting anisotropy parameters for the M45N45N45 transitions in CH3I have been compared to those calculated for the corresponding transitions in xenon, and the experimental and theoretical results are in good agreement. Anisotropy parameters have also been measured for the M45N1N45, M45N23N45, and M45N45O23 transitions. For the M45N1N45 and M45N23N45 Auger decays in CH3I, the experimentally derived angular distributions do not exhibit the strong dependence on the final ionic state that is predicted for these transitions in xenon. Resonantly excited Auger spectra have been recorded at 620.4 and 632.0 eV, coinciding with the I 3d5/2 → σ* and 3d3/2 → σ* transitions, respectively. The resulting Auger electron angular distributions for the M4N45N45 and M5N45N45 decays were found to exhibit a higher anisotropy than those for the normal process. This is due to the larger photo-induced alignment in the neutral core excited state. For a particular Auger transition, the Auger electron kinetic energy measured in the resonantly excited spectrum is higher than that in the normal spectrum. This shift, due to the screening provided by the electron excited into the σ* orbital, has been rationalized by calculating orbital ionization energies of I 3d excited and I 3d ionized states in CH3I.

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Section: N 45 O 23 and M 45 N 45 V Transitionssupporting

confidence: 86%

Auger electron angular distributions following excitation or ionization of the I 3d level in methyl iodide

Forbes

Fanis

Bomme

et al. 2018

The Journal of Chemical Physics

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“…6. We have used the available experimental [48,49,51,52] and theoretical [47,50,53] results for CH4, along with experimental [26,27] and theoretical [28] determinations of the valence shell double ionization energies of CH3I, to help guide the assignments for the principal peaks observed in the C(KVV) spectrum of CH3I. We have performed ΔSCF calculations with B3LYP functionals and an augmented quadruple zeta plus polarization basis for the double valence-hole states of CH3I2+.…”

Section: The C(kvv) Auger Electron Spectrum Of Methyl Iodidementioning

confidence: 99%

“…Pernpointner et al [28] have also calculated the double ionization energies of a number of the states lying in the 25.8-30.1 eV range and given the leading atomic contributions to the individual states. These energies have been used, shifted by 0.84 eV to higher energy so that the calculated double ionization energy (25.82 eV [28]) for the lowest state coincides with the experimental value (26.664 eV [27]), to estimate Auger electron kinetic energies for the C(KVV)…”

Section: The C(kvv) Auger Electron Spectrum Of Methyl Iodidementioning

confidence: 99%

“…The vertical lines shown in Fig. 6, representing predicted Auger electron energies, are color coded according to the atomic contributions [28]: cyan lines correspond to states having a predominantly I 5p contribution; magenta lines correspond to states having an ~64% I 5p, 16% C 2p and 3% H 1s character; and black lines correspond to states having an ~43% I 5p, 22% C 2p and 20% H 1s character. It can be seen that only those doubly charged states falling into the third category contribute significantly to the observed intensity distribution.…”

Section: The C(kvv) Auger Electron Spectrum Of Methyl Iodidementioning

confidence: 99%

“…However, CH3I spectra in this region have been recorded using dipole electron impact techniques, and provide a foundation for the present analysis. In addition, previous experimental [26,27] and theoretical [28] studies of the valence shell, single-photon double-photoionization of CH3I provide invaluable information for the assignment of the present non-resonant and resonant Auger electron spectra.…”

Section: Introductionmentioning

confidence: 98%

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Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

et al. 2020

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The dynamics of photoabsorption, photoionization, and the associated Auger decay have been investigated at the carbon K-edge in methyl iodide (CH3I) using linearly polarized synchrotron radiation. Ion yield measurements were used to investigate transitions in the pre-edge region due to excitations into either unoccupied valence or Rydberg states. The assignment of these transitions was achieved through comparison with theoretical X-ray absorption spectra calculated using time-dependent density functional theory, within the Tamm-Dancoff approximation.Several of the Rydberg states belonging to series converging onto the C 1s ionization limit exhibit significant vibrational structure that is also interpreted using theoretical calculations. The C 1s in CH3I photoelectron spectrum was measured, and the observed vibrational structure was assigned with the aid of theoretical predictions. Polarization dependent, resonantly excited, valence shell photoelectron spectra were recorded at photon energies coinciding with the C 1s → *, C 1s → 6sa1 and C 1s → 6pe transitions in CH3I, thereby allowing photoelectron angular distributions to be determined. The non-resonantly excited C(KVV) Auger electron spectrum was measured and some of the features observed at high kinetic energies were attributed to transitions into valence orbitals possessing significant iodine character. The contributions of participator and spectator Auger decay to the resonantly excited photoelectron spectra have been assessed. The influence of participator decay appears minor whereas spectator decay results in the enhanced population of satellite states.

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Calculation of the lowest electronic excitations of the alkaline earth metals using the relativistic polarization propagator

Brandt

Pernpointner

2015

Chemical Physics

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Spin–orbit effects, electronic decay and breakdown phenomena in the photoelectron spectra of iodomethane

Cited by 11 publications

References 61 publications

Auger electron angular distributions following excitation or ionization of the I 3d level in methyl iodide

Auger electron angular distributions following excitation or ionization of the I 3d level in methyl iodide

Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

Calculation of the lowest electronic excitations of the alkaline earth metals using the relativistic polarization propagator

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