TY - JOUR
T1 - Multiphoton L-shell ionization of H2S using intense x-ray pulses from a free-electron laser
AU - Murphy, B. F.
AU - Fang, L.
AU - Chen, M. H.
AU - Bozek, J. D.
AU - Kukk, E.
AU - Kanter, E. P.
AU - Messerschmidt, M.
AU - Osipov, T.
AU - Berrah, N.
PY - 2012/11/29
Y1 - 2012/11/29
N2 - Sequential multiphoton L-shell ionization of hydrogen sulfide exposed to intense femtosecond pulses of 1.25-keV x rays has been observed via photoelectron, Auger electron, and ion time-of-flight spectroscopies. Monte Carlo simulations based on relativistic Dirac-Hartree-Slater calculations of Auger decay rates in sulfur with single and double L-shell vacancies accurately model the observed spectra. While single-vacancy-only calculations are surprisingly accurate even at the high x-ray intensity used in the experiment, calculations including double-vacancy states improve on yield estimates of highly charged sulfur ions. In the most intense part of the x-ray focal volume, an average molecule absorbs more than five photons, producing multiple L-shell vacancies in 17% of photoionization events according to simulation. For 280-fs pulse duration and ∼1017 Wcm-2 focal intensity, the yield of S13+ is ∼1% of the S3+ yield, in good agreement with simulations. An overabundance of S12+, and S14+ observed in the experimental ion spectra is not predicted by either single-vacancy or double-vacancy calculations.
AB - Sequential multiphoton L-shell ionization of hydrogen sulfide exposed to intense femtosecond pulses of 1.25-keV x rays has been observed via photoelectron, Auger electron, and ion time-of-flight spectroscopies. Monte Carlo simulations based on relativistic Dirac-Hartree-Slater calculations of Auger decay rates in sulfur with single and double L-shell vacancies accurately model the observed spectra. While single-vacancy-only calculations are surprisingly accurate even at the high x-ray intensity used in the experiment, calculations including double-vacancy states improve on yield estimates of highly charged sulfur ions. In the most intense part of the x-ray focal volume, an average molecule absorbs more than five photons, producing multiple L-shell vacancies in 17% of photoionization events according to simulation. For 280-fs pulse duration and ∼1017 Wcm-2 focal intensity, the yield of S13+ is ∼1% of the S3+ yield, in good agreement with simulations. An overabundance of S12+, and S14+ observed in the experimental ion spectra is not predicted by either single-vacancy or double-vacancy calculations.
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U2 - 10.1103/PhysRevA.86.053423
DO - 10.1103/PhysRevA.86.053423
M3 - Article
AN - SCOPUS:84870573152
SN - 1050-2947
VL - 86
JO - Physical Review A - Atomic, Molecular, and Optical Physics
JF - Physical Review A - Atomic, Molecular, and Optical Physics
IS - 5
M1 - 053423
ER -