Absorption of SiH4in the Extreme Ultraviolet

Abstract

The absorption spectrum of Si${\mathrm{H}}_4$ gas has been measured in the silicon $L$ region. Three spin-orbit-split Rydberg series with sharp structure have been observed converging on the $L_{\mathrm{III},\mathrm{II}}$ edges of Si${\mathrm{H}}_4$ at 107.2 and 107.8 eV. The three series correspond in a unitedatom picture (the united atom for Si${\mathrm{H}}_4$ is argon) to transitions from a $2p$ core state to $4s$ and higher $s$ states and to $3d$ and higher $d$ states $d$ states are split into two components by the molecular field). A molecular-orbital calculation of some peak positions gives reasonable agreement with experiment.