Photoemission Cross Sections for Fragments and Molecular Ions Produced by Collisions of He(2 3S) Atoms with SiCl4 and GeCl4

Abstract

Abstract Photoemissions from excited fragments and molecular ions produced by collisions of He(2 3S) with SiCl4 and GeCl4 have been studied at the relative collision energy of 120—210 meV. Total emission cross sections in the 200—760 nm range for SiCl4 and GeCl4 are evaluated to be 4.5 ± 0.8 and 2.2 ± 0.4, respectively, in 10−20 m2 units. Emission cross sections for SiCl4+(), GeCl4+(), and Ge I atomic lines slightly decrease with increases in the collision energy. This originates from the fact that the effective potentials of He(2 3S) with SiCl4 and GeCl4 are slightly attractive. The branching ratio of Ge I states observed from GeCl4 is consistent with a simple dissociation model assuming equipartition of the available energy. These results are compatible with the harpoon mechanism as an initial step for formation of Ge I from GeCl4. The emission cross section for the SiCl(B′–X) band increases with the collision energy. This indicates that the effective potential between He(2 3S) and SiCl4 is repulsive, and that the SiCl(B′) state seems to be produced directly from SiCl4 by an excitation transfer mechanism via superexcited states.