Effects of the molecular potential on coexcitations of valence electrons in the K-shell photoeffect of 3p and 4p elements

• Published in: Physical Review A
• Main Authors: Hauko, Robert, Padežnik Gomilšek, Jana, Kodre, Alojz, Arčon, Iztok, Aquilanti, Giuliana
• Format: Other/Unknown Material
• Language: English
• Published: 2019
• Subjects: X-ray absorption spectra; gaseous hydrides; 3p K-edge spectra; DFT; rentgentski žarki; absorpcijski spekter; plinski hidridi; fotoabsorpcija; Hartree; Orca
• Online Access: http://repozitorij.ung.si/IzpisGradiva.php?id=4719; https://plus.si.cobiss.net/opac7/bib/22395158?lang=sl

Photoabsorption spectra of gaseous hydrides of 3p (PH3, H2S, HCl) and 4p elements (GeH4, AsH3 , H2Se, HBr) are measured in the energy region within 50 eV above the K edge, to study coexcitations of valence electrons by photoeffect in the K shell. The analysis of the valence coexcitations is extended to Ar, Kr, and SiH4. Relative probabilities and energies of states in the individual coexcitation channels are recovered by modeling the spectral features with a minimal ansatz based on the features in the contiguous noble gas. The extracted parameters are compared to the results of theoretical calculations for molecules (ORCA code) and free atoms (Hartree-Fock code). The experimental results confirm that the valence coexcitations in the 3p and 4p hydride molecules can be satisfactorily described by a two-step process, with the shake of the outer electron following the excitation of the core electron. The total probability—relative to the K-edge jump—of the shake-up processes shows a steady decrease from 19% in Si to 14% in Cl, and from 15% in Ge to 12% in Br. The experimental values for Ar (12%) and Kr (10%) are in accord with the trend. The dominant contribution is the transition to quasiatomic orbitals, in contrast with the deeper coexcitation channels in hydride molecules where transition to molecular orbitals prevails.