PENNING IONIZATION OF CH3SCN, CH3NCO, AND CH3NCS BY COLLISION WITH HE-ASTERISK(2(3)S) METASTABLE ATOMS

Penning ionization of CH3SCN, CH3NCO, and CH3NCS upon collision with H e(2S-3) metastable atoms was studied by collision-energy resolved Pen ning ionization electron spectroscopy. Collision energy dependence of the partial ionization cross sections indicates that the interaction p otentials are strongly anisotropic between He(2S-3) and the pseudohal ides investigated. In the studied energy range, the interaction potent ial was found to be repulsive around the methyl and attractive around the pseudohalide group. The ionization cross section of the ''lone pai r'' sigma electrons localized on the nitrogen, oxygen, and sulfur atom in CH3SCN, CH3NCO, and CH3NCS, respectively, was found to be very enh anced in the Penning ionization electron spectroscopy.