Enhanced production of excited neutrals following core-to-Rydberg excitation in molecules: SiCl4

Abstract

Using monochromatized synchrotron radiation in the range 103 to 112 eV we have monitored the dispersed UV/optical fluorescence resulting from excitation of a Si 2p electron in SiCl4. The main features in the fluorescence spectrum have been identified as emission from the SiCl4+ C state and from excited Si atoms. Features in the fluorescence excitation spectra are assigned to excitation of a Si 2p electron to unoccupied valence and Rydberg orbitals. For the SiCl4+ C state emission there is significant enhancement in the yield following excitation to valence orbitals and very little enhancement as a result of Rydberg excitation. The opposite is true for emission from excited Si atoms. Enhancement in the SiCl4+ C state production upon valence excitation results from autoionization of the core-excited state. The relatively large yield of excited Si atoms following Rydberg excitation is due to the greater probability of the core-excited Rydberg state decaying, via a resonant Auger process, to highly excited, unbound states of SiCl4+. The molecular ion then fragments before the excited Rydberg electron can relax.