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Medientyp:
E-Artikel
Titel:
Ultrafast absorption of intense x rays by nitrogen molecules
Beteiligte:
Buth, Christian;
Liu, Ji-Cai;
Chen, Mau Hsiung;
Cryan, James P.;
Fang, Li;
Glownia, James M.;
Hoener, Matthias;
Coffee, Ryan N.;
Berrah, Nora
Erschienen:
AIP Publishing, 2012
Erschienen in:The Journal of Chemical Physics
Sprache:
Englisch
DOI:
10.1063/1.4722756
ISSN:
0021-9606;
1089-7690
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p>We devise a theoretical description for the response of nitrogen molecules (N2) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations (ΔSCF method). To describe the interaction with N2, a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N2: a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of \documentclass[12pt]{minimal}\begin{document}${\rm N}_2^{2+}$\end{document}N22+, and molecular fragmentation are explained.</jats:p>