Resonances in photoabsorption spectra of ${\mathrm{SiF}}_4$, Si(${\mathrm{CH}}_3$${)}_4$, and ${\mathrm{SiCl}}_4$ near the silicon K edge

Photoabsorption spectra of tetrachlorosilane, tetramethylsilane, and tetrafluorosilane have been measured using synchrotron radiation in the 1830–1900-eV photon-energy range, i.e., in the vicinity of the silicon 1s edge. Intense resonances are observed in the discrete and the continuum part of the spectrum, and compared with previously published photoabsorption spectra obtained near the silicon 2s and 2p edges. Resonances in the discrete part of the spectrum are qualitatively interpreted using structural and electronic properties of the core-equivalent P$X_4$ (X=F, ${\mathrm{CH}}_3$, or Cl) phosphoranyl radicals. The interpretation of features in the continuum are discussed in terms of shape resonances, within the tetrahedral geometry.