Energy partitioning in photodissociation of methyl, ethyl and n-propyl iodides at 304 nm Original Research Article

The energy partitioning in photodissociation of n-alkyl iodides has been studied by state-selective photofragment translational spectroscopy combined with a pulsed molecular beam at 304 nm. Translational energies of photofragments are obtained by analyzing the time-of-flights of two product channel iodine atoms, i.e., I(2P32) and I∗(2P12) for CH3I, C2H5I and C3H7I. The average energy disposed into the internal mode (Eint) of alkyl radicals has shown an increasing tendency from 17% for the I∗ channel of CH3I to 53% for the I channel of n-C3H7I and is estimated to further increase to 76% for the I∗ channel of C4H9I. The methyl radical in CH3I photolysis has shown the vibrational excitation in its umbrella mode. The distribution peaks have appeared at ν=2 for I∗ and ν=4 for I product channels, respectively. The observed results are compared with a classical impulsive description dynamics. The energy partitioning is found to be very little dependent on the excitation wavelength for photodissociation all over the A-band region.