In situ photolysis of CD₃i in solid orthodeuterium

Photochemical reactions of molecules in solid orthodeuterium (o-D ₂) have been studied by high-resolution infrared spectroscopy and compared with previous results obtained in solid parahydrogen (p-H₂). Ultraviolet photolysis of CD₃I molecules in solid o-D₂ yielded CD₃ radicals and iodine atoms efficiently, which indicates a small cage effect in solid o-D₂, as in the case of solid p-H ₂. The Fourier transform infrared spectrum of the ν₃ vibrational band of CD₃ showed a rotational structure with additional splitting due to crystal field interactions. The magnetic dipole transition (²P_1/2←²P_3/2) of the I atom isolated in solid o-D₂ was observed together with a strong rotational satellite of deuterium molecules through the electron-roton coupling in solid hydrogen. The tunneling reaction between CD₃ and D₂ was not observed in a time scale of a few days, which gives the upper limit of the tunneling reaction rate of 10^-8 s^-1 at 4.2 K.