PHOTOABSORPTION AND FLUORESCENCE CROSS-SECTIONS OF SICL4 IN THE REGION OF 6.2-31 EV

Absolute photoabsorption and fluorescence cross sections of gaseous Si Cl4 have been measured in the energy region 6.2-31 eV using synchrotro n 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 n m). Emissions have been observed for the (C) over tilde T-2(2)-->(A) o ver tilde T-2(2) and (C) over tilde T-2(2)-->(X) over tilde T-2(1) pro cesses 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 r adical. 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 sectio n for formation of the (C) over tilde T-2(2) ionic state [Carlson et a l., J. Chem. Phys. 84, 641 (1986)], it has been concluded that the SiC l4+((C) over tilde T-2(2)) formed decays via radiative processes with quantum yield phi approximate to 1. The experimental results provide i nformation 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 an d 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 1 8.17+/-0.03 eV, respectively. (C) 1997 American Institute of Physics.