Journal of Chemical Physics, Vol.106, No.12, 4853-4859, 1997
Photoabsorption and Fluorescence Cross-Sections of Sicl4 in the Region of 6.2-31 eV
Absolute photoabsorption and fluorescence cross sections of gaseous SiCl4 have been measured in the energy region 6.2-31 eV using synchrotron radiation as the light source. Higher order light from the 1-m Seya monochromator was suppressed by use of an Ar gas filter in the energy range 11.3-15.5 eV (110-80 nm) and a LiF window at hv < 11.8 eV (105 nm). Emissions have been observed for the (C) over tilde T-2(2)-->(A) over tilde T-2(2) and (C) over tilde T-2(2)-->(X) over tilde T-2(1) processes of the SiCl4+ molecular ion and the (A) over tilde B-1(1)-->(X) over tilde (1)A(1) and B-3(1)-->(X) over tilde (1)A(1) of the SiCl2 radical. The total fluorescence cross section has been determined to be 22.4+/-1.0 Mb at 21.22 eV. By comparing with the partial cross section for formation of the (C) over tilde T-2(2) ionic state [Carlson et al., J. Chem. Phys. 84, 641 (1986)], it has been concluded that the SiCl4+((C) over tilde T-2(2)) formed decays via radiative processes with quantum yield phi approximate to 1. The experimental results provide information on the breakdown pathways of the SiCl4+((C) over tilde T-2(2)) ion state. The bands observed in photoabsorption and fluorescence excitation spectra have been assigned as the (4s, np, and np’)<--3t(2), (4s and np)<--1e, (4s and np)<---1e, (4s and 4p)<--2t(2), and (np and nd)<--2a(1) Rydberg series. The ionization energies for the (2t(2))(-1) and (2a(1))(-1) processes have been found to be 15.04+/-0.03 and 18.17+/-0.03 eV, respectively.
Keywords:TETRACHLORO MOLECULAR-IONS;ELECTRONIC EMISSION;ABSORPTION-SPECTRA;STATES;SPECTROSCOPY;DYNAMICS;RADICALS;SIF4