ELECTRON-SPIN-RESONANCE STUDIES OF THE METHANE RADICAL CATIONS ((CH4-C-12,13, (CDH3+)-C-12,13, (CD2H2+)-C-12, (CD3H+)-C-12, (CD4+)-C-12) INSOLID NEON MATRICES BETWEEN 2.5 AND 11 K - ANALYSIS OF TUNNELING())

The radical cation of-methane isolated in neon matrices exhibits highl y unusual electron spin resonance (ESR) spectral features between 2.5 and 11 K. The anomaly has been clarified by invoking large amplitude t unneling motions of the hydrogens among several symmetrically equivale nt Jahn-Teller distorted structures. The effect of the tunneling motio ns upon the ESR spectrum was investigated by an analysis scheme based upon permutation-inversion group theory. All the deuterium substituted cations, i.e., CDH3+, CD2H2+, CD3H+, and CD4+ were also studied. The hyperfine coupling constant of C-13 was obtained from the study of (CD H3+)-C-13 and (CH4+)-C-13. Several independent generation methods were employed during the course of these methane cation studies, including photoionization, electron bombardment, x-irradiation, and a pulsed la ser surface ionization technique. (C) 1995 American Institute of Physi cs.