Infrared spectroscopy of rovibrational transitions of methyl radicals (CH 3, CD 3) in solid parahydrogen

Abstract

The ν 3 and ν 4 vibrational transitions of CH 3 and CD 3 isolated in solid parahydrogen were studied by high-resolution infrared spectroscopy. The radicals were produced by in situ UV photolysis of methyl iodides trapped in solid parahydrogen. The observed spectra showed clear rotational fine structures, which were subjected to further splitting due to the electrostatic field of solid parahydrogen. The molecular constants and crystal field parameters of the radicals in solid parahydrogen were determined by analyzing the spectral structures of the ν 3 and ν 4 transitions of CD 3 by the crystal field theory. The rotational constants of the CD 3 radical were found to be only a few percent smaller than those in the gas phase. The determined crystal field parameters indicated significant quantum effects in the intermolecular interactions between the radicals and hydrogen molecules in solid parahydrogen.