Abstract
Both the L- and K-edge x-ray-absorption near-edge spectra for the five compounds Si(( (x=0 to 4) are reported. The spectra of the two end members of the series, Si( and Si(, are compared to the spectra of their respective solid-state analogs, and SiC. The L-edge spectra of gaseous Si( and solid are qualitatively identical; while the L-edge spectra of gaseous Si( and its solid-state counterpart, SiC, show strong similarities. MS-Xα calculations were performed for the two species Si( and Si( for the Si 2p, 2s, and 1s regions and used to assign the spectra for both compounds. By comparison of molecular-orbital diagrams of Si( and , the first two transitions in the L-edge spectra of have been assigned to transitions from the Si 2p to orbitals of and symmetry. In addition to , the L-edge spectra of the isoelectronic species , , and are also assigned in a similar manner. Compared to the L edge, the K-edge region of the gas-phase compounds is found to have less in common with the spectra of the solid-state analogs. In the K-edge region, peaks from the extended band structure and/or multiple scattering are evident in the solid-state compounds. These peaks are not present, as expected, in the gas-phase models or in the theoretical calculations on the gas-phase compounds. These multiple-scattering peaks are not seen in the L-edge solid-state spectra because of the strong shape resonances peaks in this region.
- Received 3 May 1993
DOI:https://doi.org/10.1103/PhysRevB.48.14989
©1993 American Physical Society