Gas-to-cluster effects in S 2p-excited SF6

Abstract

High resolution X-ray spectroscopic studies on free SF6 molecules and SF6 clusters near the S 2p ionization thresholds are reported. Spectral changes occurring in clusters for the intense molecular-like S 2p1/2,3/2 → 6a1g-, 2t2g-, and 4eg-resonances are examined in detail. Neither gas-to-cluster spectral shifts nor changes in peak shape are observed for the pre-edge 6a1g-band. Significant changes in band shape and distinct gas-to-cluster shifts occur in the S 2p1/2,3/2 → 2t2g- and 4eg-transitions. These are found in the S 2p-ionization continua. The quasiatomic approach is used to assign the experimental results. It is shown that a convolution of asymmetric and symmetric contributions from Lorentzian and Gaussian line shapes allows us to model the spectral distribution of oscillator strength for the S 2p1/2,3/2 → 2t2g-, and 4eg-transitions. The asymmetry is due to trapping of the photoelectron within the finite size potential barrier. The Lorentzian contribution is found to be dominating in the line shape of the S 2p → 2t2g- and 4eg-bands. The spectroscopic parameters of the spin-orbit components of both the 2t2g- and 4eg-bands are extracted and their gas-to-cluster changes are analyzed. The photoelectron trapping times in free and clustered SF6 molecules are determined. Specifically, it is shown that spectral changes in clusters reflected in core-to-valence-transitions are due to a superposition of the singly scattered photoelectron waves at the neighboring molecules with the primary and multiply scattered waves within the molecular cage.

Local electronic structure and nanolevel hierarchical organization of bone tissue: theory and NEXAFS study

“…The observed large HAP-tobone red shift δE P3s ≈0.9 eV confirms its relation with the effect of super periodicity on the band structure of HAP. This assignment is also supported by the recent investigation [67], where it is shown that, in contrast to the shape resonances, the pre-edge states in molecular solids and crystals containing chemical stable molecular-like groups demonstrate minor sensitivity to the surroundings of the core-excited atom.…”

“…The P / / -2p 1 3 2,1 2 e * and t 2 * states located above the edge are usually attributed to the shape resonances (see, e.g. [67]). The P 2p NEXAFS of native and heated bone and HAP [31,53] provides an additional sensitive probe of the hierarchy induced changes in electronic structure of bone tissue.…”

The peculiarities of charge distribution and spatiotemporal changes in electronic and atomic structure of bone tissue

“…The nearly Gaussian shape of the Ca 2+ 2p 3/2 −1 and 2p 1/2 1 PE lines is associated with the bandwidth of the photon source, the inhomogeneous imperfectness and size distribution of crystallites as well as with the quadratic intra-and intercrystallite displacements. 35 The extracted Gaussian widths W G are given in parenthesis in Table 1. The Lorentzian widths are about 0.1 eV and can be reasonably assigned with the Ca 2+ 2p-hole live time.…”

“…The contributions of asymmetric Lorentzian associated with the PE trapping time (the multiple scattering effects) 35 are negligibly weak.…”