Electronic-state interference in the C 
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 excitation and decay of methyl chloride studied by angularly resolved Auger spectroscopy

Nandi, Saikat; Nicolas, Christophe; Artemyev, A. N.; Novikovskiy, N. M.; Miron, Catalin; Bozek, John D.; Demekhin, Ph. V.

doi:10.1103/physreva.96.052501

Cited by 9 publications

(14 citation statements)

References 61 publications

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“…The calculations performed by Nandi et al show that the average angular distribution for all the unresolved spectator resonant Auger electrons is almost isotropic, regardless of excitation energy [61]. This prediction appears consistent with the experimental results on both CH3Cl and CH3I.…”

Section: Valence Shell Photoelectron Spectrasupporting

confidence: 63%

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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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Section: Valence Shell Photoelectron Spectrasupporting

confidence: 63%

“…The comparison of the resonantly excited valence shell photoelectron spectra of CH3I recorded in the present study with the analogous spectra for CH3Cl measured by Nandi et al [61] is informative. We consider specifically the spectra arising from the C 1s → * and C 1s → pe transitions.…”

Section: Valence Shell Photoelectron Spectrasupporting

confidence: 57%

Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

et al. 2020

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“…where b L pj are known kinematic coefficients. The impact of Fano interferences on anisotropy parameters β 2 of high-energy photoelectrons in molecules is well documented [18][19][20][21][22][23][24][25]. In the off-resonance excitation regime, anisotropy in the photoemission is governed by the direct ionization channel, while in the on-resonance regime, it is determined by the resonant channel (the first and second terms in the amplitude (1), respectively).…”

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confidence: 99%

“…In the off-resonance excitation regime, anisotropy in the photoemission is governed by the direct ionization channel, while in the on-resonance regime, it is determined by the resonant channel (the first and second terms in the amplitude (1), respectively). This induces a rather broad dispersion of the β 2 parameter across the resonance [18][19][20][21][22][23][24][25]. The Fano interference, i.e.…”

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confidence: 99%

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Recovery of High-Energy Photoelectron Circular Dichroism through Fano Interference

et al. 2019

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It is commonly accepted that the magnitude of a photoelectron circular dichroism (PECD) is governed by the ability of an outgoing photoelectron wave packet to probe the chiral asymmetry of a molecule. To be able to accumulate this characteristic asymmetry while escaping the chiral ion, photoelectrons need to have relatively small kinetic energies of up to a few tens of electron volts. Here, we demonstrate a substantial PECD for very fast photoelectrons above 500 eV kinetic energy released from methyloxirane by a participator resonant Auger decay of its lowermost O 1s-excitation. This effect emerges as a result of the Fano interference between the direct and resonant photoionization pathways, notwithstanding that their individual effects are negligibly small. The resulting dichroic parameter has an anomalous dispersion, i.e. it changes its sign across the resonance, which can be considered as an analogue of the Cotton effect in the X-ray regime. 32.80.Hd, 33.55.+b, 81.05.Xj Photoelectron circular dichroism (PECD) is a fundamental chiroptical effect causing a forward-backward asymmetry in the laboratory-frame angular distribution of photoelectrons emitted from chiral molecules in the gas phase. PECD was first predicted theoretically for one-photon ionization [1-3] and then verified in pioneering experiments with circularly polarized synchrotron radiation [4,5]. The effect persists also in the multiphoton ionization regime using intense laser pulses [6,7]. Because PECD is a pure electric-dipole effect, it is much stronger than the traditional CD in the photoabsorption spectra of chiral molecules [8]. This fact, together with its enantioselectivity, has established PECD as a powerful tool for chiral recognition in the gas phase [8][9][10][11].Ritchie [1-3] has proven analytically that PECD arises due to an incomplete compensation of the contributions from emitted partial electron waves with different projections ±m of the carried angular momentum ℓ. Such an inequivalence occurs only for chiral molecules and has a twofold origin: It is induced by the chiral asymmetries of both, the initial bound and the final continuum electronic states entering the dipole-transition amplitudes. For slow photoelectrons with kinetic energies of a few electron volts, initial and final state contributions to PECD can be comparable [12]. As the electron kinetic energy grows, the photoelectron wave packet escapes the molecular ion quickly and does not have enough time to adopt its chiral asymmetry. In other words, both, the chiral initial state and the chiral potential of the ion can be considered almost symmetric for very fast photoelectrons. As a consequence, at high kinetic energies, typically at a few tens of electron volts [12,13] and in extreme cases at about 70 eV [14], PECD vanishes.In the present work, we demonstrate a very general mechanism of PECD recovery for electrons with kinetic energies of as high as a few hundreds of electron volts. This scenario involves an intermediate electronic resonance, which enables an excited m...

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Photoionization of the I 4d and valence orbitals of methyl iodide

Forbes

Fanis

Rolles

et al. 2020

J. Phys. B: At. Mol. Opt. Phys.

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The photoabsorption and photoionization dynamics of the I 4d and valence orbitals in methyl iodide have been studied both experimentally and theoretically. Synchrotron radiation has been employed to measure the total ion yield in the vicinity of the I 4d ionization thresholds. The observed structure, due to excitations into Rydberg or valence states, has been assigned using transition energies and relative intensities computed with time-dependent density functional theory within the Tamm–Dancoff approximation. Photoelectron spectra, recorded with plane polarized radiation in two polarization geometries, have allowed the effect of autoionization on the valence electron angular distributions to be investigated. The spectra obtained at photon energies of 50.62 and 52.34 eV, coinciding respectively with the I 4d5/2 → σ* and 4d3/2 → σ* transitions, reveal, in addition to valence shell photoelectron bands, features not associated with simple photoionization of the parent molecule. High resolution photoelectron spectra of the I 4d main-lines display structure resulting from spin–orbit coupling and molecular field splitting. The binding energies of the five states contributing to the (I 4d)−1 ionization have been determined. The iodine (in CH3I) N45VV Auger spectrum has been measured and the observed structure has been assigned using the core hole binding energies derived in the present work together with established ionization energies of the doubly charged ion. The experimentally determined Auger electron angular distributions have been discussed in relation to the theoretical angular distribution parameter characterizing the spatial alignment of molecular axes in the (I 4d)−1 state.

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Electronic-state interference in the C 1s excitation and decay of methyl chloride studied by angularly resolved Auger spectroscopy

Cited by 9 publications

References 61 publications

Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

Recovery of High-Energy Photoelectron Circular Dichroism through Fano Interference

Photoionization of the I 4d and valence orbitals of methyl iodide

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