Hidden double excitations in the oxygen inner-shell ionization continuum of CO (original) (raw)
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Influences from the C1sshape resonance on the vibrational progression in the Auger decay of CO
Physical Review A, 1998
Auger decay from the C 1s core-ionized state of CO has been studied with vibrational resolution both at the C 1s shape resonance and far above. Variations in the vibrational intensity distribution with photon energy are observed. This observation is explained solely by the modified vibrational envelope of the core-ionized intermediate state at the shape resonance maximum, as demonstrated in a numerical simulation. This implies that the temporary trapping of the photoelectron at the shape resonance does not significantly affect the deexcitation process. Thus the deexcitation step is described by the Franck-Condon principle even at the shape resonance. The angular anisotropy of the Auger decay at the shape resonance has also been studied with vibrational resolution. Weak dependence upon the final state and no detectable influence from the vibrational quanta is observed. ͓S1050-2947͑98͒03409-X͔
Interatomic Auger decay in CO molecule
Journal of Electron Spectroscopy and Related Phenomena, 2007
Energy spectra of electrons ejected in electron impact on CO molecules have been measured for the incident electron energy 1400 eV. The aim was to study the interatomic Auger transitions resulted from the filling in the O K-shell hole by a C K-shell electron. The corresponding peaks have been identified and their relative transition probabilities (partial widths) measured. Theoretical widths of these transitions calculated in the Hartree-Fock approximation are in good agreement with the experimental data.
Physical Review A, 2002
We report an experimental investigation of higher vibrational levels (ЈϾ2) of the C 1s→* excitation in CO utilizing resonant Auger electron spectroscopy. These vibrational states are not readily seen in a total yield absorption spectrum, whereas they are shown to be discernable in a partial electron yield spectrum. Furthermore, the nature of the spectator part between E Bin ϭ26.5 and 30 eV, being subject of an ongoing debate, is discussed on the grounds of the presented experimental data. The experiments indicate that the formally used adiabatic framework for the multitude of close lying 2 ⌸ potential curves is inappropriate, but that a diabatic treatment can be used for the interpretation of the spectra.
Resonant double Auger decay in carbon K-shell excitation of CO
Physical Review A, 2008
We have studied double Auger decay after C 1s → 2 ء photoexcitation in gas phase carbon monoxide. Two distinct processes, namely direct double Auger decay and cascade double Auger decay, are identified and studied in detail using multiple coincidence techniques. Cascade Auger decay is shown to be the overall dominant process. Decay channels involving the dissociation of the molecule followed by autoionization of the oxygen fragments are observed.
“Hidden” vibrations in CO: Reinvestigation of resonant Auger decay for the C 1 s→ π* excitation
We report an experimental investigation of higher vibrational levels (ЈϾ2) of the C 1s→* excitation in CO utilizing resonant Auger electron spectroscopy. These vibrational states are not readily seen in a total yield absorption spectrum, whereas they are shown to be discernable in a partial electron yield spectrum. Furthermore, the nature of the spectator part between E Bin ϭ26.5 and 30 eV, being subject of an ongoing debate, is discussed on the grounds of the presented experimental data. The experiments indicate that the formally used adiabatic framework for the multitude of close lying 2 ⌸ potential curves is inappropriate, but that a diabatic treatment can be used for the interpretation of the spectra.
New insight into the Auger decay process in O2: The coincidence perspective
Journal of Electron Spectroscopy and Related Phenomena, 2012
Photoelectron-Auger electron coincidence spectroscopy is a powerful tool for the investigation of Auger decay processes with different core-ionized intermediate states. In this paper we describe an investigation into the Auger decay of the O 2 molecule, with the purpose of bringing new insight into the dynamics of the core hole decay mechanism. Using a novel experimental approach to measuring such coincidence spectra we report the highest resolution Auger spectrum of O 2 recorded hitherto. In our approach, we have combined the advantages of these coincidence spectra with the high resolution and excellent signal-to-noise ratios of non-coincident Auger spectra and a state-of-the-art fit analysis. In this way we have derived information about the potential energy curves of the final states W 3 u , B 3 g , and B' 3 u and concluded that the corresponding Auger transitions are formed to a large part by strongly overlapping vibrational progressions. The present findings are compared to earlier results reported in the literature confirming some theoretical predictions.
Separating the Vibrationally Resolved Auger Decay Channels for a CO Core Hole State
Physical Review Letters, 2008
The K-VV Auger spectrum of carbon monoxide (CO) excited by C 1s photoionization has been investigated with a novel electron-electron coincidence setup. The energy resolution is sufficiently high to resolve the vibrational energy levels of the core-ionized intermediate state and of most dicationic final states in the two-dimensional electron energy map. We demonstrate how the influence of vibrational states on a molecular Auger spectrum can be accessed experimentally without the constraint of averaging over all intermediate state energies.
Multichannel resonance processes: Theory and application to the Auger spectra of the CO molecule
Physical Review A, 1993
A general expression for predicting vibrational profiles of a molecular Auger spectrum is derived. The relationship between a "theoretical" cross section and an experimental spectrum is discussed and specific procedures for implementing cross-section calculations in the Born-Oppenheimer approximation are proposed. The carbon and oxygen K-LL Auger spectra of CO are reproduced on the entire energy range of interest and specific spectral regions are analyzed in greater detail. The results are compared with experimental data.
Resonant Auger decay of the core-excited C^{*}O molecule in intense x-ray laser fields
Physical Review A, 2011
The dynamics of the resonant Auger (RA) process of the core-excited C * O(1s −1 π * , v r = 0) molecule in an intense X-ray laser field is studied theoretically. The theoretical approach includes the analogue of the conical intersections of the complex potential energy surfaces of the ground and 'dressed' resonant states due to intense X-ray pulses, taking into account the decay of the resonance and the direct photoionization of the ground state, both populating the same final ionic states coherently, as well as the direct photoionization of the resonance state itself. The light-induced non-adiabatic effect of the analogue of the conical intersections of the resulting complex potential energy surfaces gives rise to strong coupling between the electronic, vibrational and rotational degrees of freedom of the diatomic CO molecule. The interplay of the direct photoionization of the ground state and of the decay of the resonance increases dramatically with the field intensity. The coherent population of a final ionic state via both the direct photoionization and the resonant Auger decay channels induces strong interference effects with distinct patterns in the RA electron spectra. The individual impact of these physical processes on the total electron yield and on the CO + (A 2 Π) electron spectrum are demonstrated.