RESONANCE RAMAN-SPECTRA OF PHOTODISSOCIATING CH3I AND CD3I IN SOLUTION

Raman spectra of CH3I and CD3I in hexane, including absolute cross sections for CH3I, have been obtained using 266 nm excitation, on resonance with the directly dissociative 3Q0 state. Both isotopic species exhibit long vibrational progressions in the C-I stretch and its combination bands with the methyl umbrella mode. The relative intensities of the C-I overtones in CH3I are similar in vapor and solution phases, indicating that the early photodissociation dynamics are not greatly altered by solvation. The higher overtone transitions are significantly broadened and shifted to lower frequencies in solution. The absorption spectra and resonance Raman intensities of CH3I have been simulated by parameterizing an uncoupled two-oscillator model in which the C-I stretch is taken as a Morse oscillator in the ground state with an exponential repulsive potential in the excited state. © 1990.