15min:

YUKI MIYAMOTO, Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan; AND TAKAMASA MOMOSE, Department of Chemistry, The University of British Columbia, Vancouver, B.C., V6T1Z1, Canada.

Infrared spectra of the chloromethyl radical (CH₂Cl) isolated in solid parahydrogen has been reported. The radical was produced by in situ UV photolysis of chloroiodomethane (CH₂ClI) in solid parahydrogen. Infrared absorption of the ₃ (CCl stretch), ₂ (CH₂ scissors), and ₁ (CH₂ symmetric-stretch) modes of CH₂Cl were clearly observed. The matrix shift of the ₁ band is -6 cm^-1 relative to the gas phase band origin. Fine spectral features in the infrared absorption spectra reveal that the radical exhibits uni-axial quantized rotation along molecular a -axis in solid parahydrogen. The temporal change of the infrared absorption intensity indicates that the nuclear spin conversion between para (I=0) and ortho (I=1) spin modifications of the radical takes place in solid parahydrogen at 3.6 K. The conversion rate was determine to be 0.0046 min^-1, which is comparable to the conversion rate between the J=1, I=1 and J=0, I=2 states of CH₄ in solid parahydrogen. We did not observe any significant change of the intensity of the CH₂Cl radical for a few days in solid parahydrogen, which indicates that there is no tunneling reaction between CH₂Cl and H₂ at 3.6 K.