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Title: Resonant Auger decay of the core-excited C{sup *}O molecule in intense x-ray laser fields

Abstract

The dynamics of the resonant Auger (RA) process of the core-excited C*O(1s{sup -1}{pi}*,v{sub r}=0) molecule in an intense x-ray laser field is studied theoretically. The theoretical approach includes the analog 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 nonadiabatic effect of the analog 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{sup +}(A {sup 2}{Pi}) electron spectrum aremore » demonstrated.« less

Authors:
; ;  [1]
  1. Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22068736
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 84; Journal Issue: 3; Other Information: (c) 2011 American Institute of Physics; Country of input: Syrian Arab Republic
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; CARBON MONOXIDE; COBALT IONS; DECAY; DEGREES OF FREEDOM; ELECTRON SPECTRA; ELECTRONS; GROUND STATES; INTERFERENCE; MOLECULES; PHOTOIONIZATION; POPULATION INVERSION; POTENTIAL ENERGY; PULSES; RESONANCE; STRONG-COUPLING MODEL; SURFACES; VISIBLE RADIATION; X RADIATION; X-RAY LASERS

Citation Formats

Demekhin, Philipp V., Chiang, Ying-Chih, and Cederbaum, Lorenz S. Resonant Auger decay of the core-excited C{sup *}O molecule in intense x-ray laser fields. United States: N. p., 2011. Web. doi:10.1103/PHYSREVA.84.033417.
Demekhin, Philipp V., Chiang, Ying-Chih, & Cederbaum, Lorenz S. Resonant Auger decay of the core-excited C{sup *}O molecule in intense x-ray laser fields. United States. doi:10.1103/PHYSREVA.84.033417.
Demekhin, Philipp V., Chiang, Ying-Chih, and Cederbaum, Lorenz S. Thu . "Resonant Auger decay of the core-excited C{sup *}O molecule in intense x-ray laser fields". United States. doi:10.1103/PHYSREVA.84.033417.
@article{osti_22068736,
title = {Resonant Auger decay of the core-excited C{sup *}O molecule in intense x-ray laser fields},
author = {Demekhin, Philipp V. and Chiang, Ying-Chih and Cederbaum, Lorenz S.},
abstractNote = {The dynamics of the resonant Auger (RA) process of the core-excited C*O(1s{sup -1}{pi}*,v{sub r}=0) molecule in an intense x-ray laser field is studied theoretically. The theoretical approach includes the analog 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 nonadiabatic effect of the analog 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{sup +}(A {sup 2}{Pi}) electron spectrum are demonstrated.},
doi = {10.1103/PHYSREVA.84.033417},
journal = {Physical Review. A},
number = 3,
volume = 84,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2011},
month = {Thu Sep 15 00:00:00 EDT 2011}
}
  • The resonant Auger process is studied in intense x-ray laser fields. It is shown that the dressing of the initial and decaying states by the field leads to coupled complex potential surfaces which, even for diatomic molecules, possess intersections at which the nonadiabatic couplings are singular. HCl is studied as an explicit showcase example. The exact results differ qualitatively from those without rotations. A wealth of nonadiabatic phenomena is expected in decay processes in intense x-ray fields.
  • The theory of resonant Auger decay of atoms in a high-intensity coherent x-ray pulse is presented. The theory includes the coupling between the ground state and the resonance due to an intense x-ray pulse, taking into account the decay of the resonance and the direct photoionization of the ground state, both populating the final ionic states coherently. The theory also considers the impact of the direct photoionization of the resonance state itself which typically populates highly excited ionic states. The combined action of the resonant decay and of the direct ionization of the ground state in the field induces amore » non-Hermitian time-dependent coupling between the ground and the ''dressed'' resonance stats. The impact of these competing processes on the total electron yield and on the 2s{sup 2}2p{sup 4}({sup 1}D)3p {sup 2}P spectator and 2s{sup 1}2p{sup 6} {sup 2}S participator Auger decay spectra of the Ne 1s{yields}3p resonance is investigated. The role of the direct photoionization of the ground state and of the resonance increases dramatically with the field intensity. This results in strong interference effects with distinct patterns in the electron spectra, which differ for the participator and spectator final states.« less
  • In this work we report the modification of the normal Auger line shape under the action of an intense x-ray radiation. Under strong Rabi-type coupling of the core, the Auger line profile develops into a doublet structure with an energy separation mainly determined by the relative strength of the Rabi coupling. In addition, we find that the charge resolved ion yields can be controlled by judicious choice of the x-ray frequency.
  • The decay properties of an above-threshold resonance in core-ionized water, which is difficult to identify with usual spectroscopic methods, have been analyzed by resonant Auger spectroscopy. The resonance is shown to correspond to a doubly excited neutral state embedded in the O 1s ionization continuum. The main result of the experiments is the assessment on the dissociative nature of the intermediate state, with a consequent fragmentation in H neutral plus O*H core excited. This dissociation takes place on the same time scale as electron decay, and therefore is categorized as an ultrafast dissociation process.
  • The valence character of O 1s{yields}Rydberg excited O{sub 2} is investigated by means of participator Auger decay spectroscopy, performed at selected photon energies across the K-shell resonance region, and by means of partial ion yield x-ray absorption spectroscopy. For several of the excitation energies studied, the authors find substantial {sigma}{sup *}({sup 4}{sigma}{sub u}{sup -},{sup 2}{sigma}{sub u}{sup -}) valence character being mixed with ns{sigma} and np{sigma} ({sup 4}{sigma}{sub u}{sup -},{sup 2}{sigma}{sub u}{sup -}) Rydberg states. An experimental indication of a coupling between the channels associated with quartet and doublet ion cores is considered and discussed. New spectroscopic constants are derived formore » the singly ionized X {sup 2}{pi}{sub g} state of O{sub 2} based on the observation of at least 20 vibrational sublevels.« less