Calculation of the frequencies and intensities in the infrared spectrum of the ethyl radical

The infrared spectra of matrix isolated ethyl radicals have been simulated by a normal coordinate calculation, fitting the vibrational frequencies of all, partially and fully deuterated species CH3CH2⋅, CH3CD2⋅, CD3CH2⋅, and CD3CD2⋅, together with the calculation of the IR intensities by modified CNDO and INDO open shell procedures. A good reproduction of the observed spectra is in agreement with the theoretical molecular geometry and the special structural features shown by deviations of the force constants for the ethyl radical compared to that of related saturated and unsaturated hydrocarbons.