Emission spectroscopy of photodissociating CH3I and CD3I

Emission spectra from photodissociating CH3I and CD3I are recorded following excitation with 266-nm light. The emission wavelengths and relative intensities to the ground vibrational states are tabulated. A time-dependent formalism is used to interpret the data in terms of vibrational wave functions of the ground electronic state of methyl iodide and the dynamics of photodissociation on an electronic excited state. The observed intensities in the CD3I spectra are perturbed by a Fermi resonance between two quanta of C-I stretch and one quantum of umbrella bend. Both CH3I and CD3I photodissociate with initial motion in the C-I stretching coordinate and subsequent motion in the umbrella coordinate to form the planar CH3/CD3 products. The qualitative mechanisms described here are consistent with a more detailed theoretical treatment presented in the following paper