Photodissociation of Methyl Iodide via Selected Vibrational Levels of the (B)over-tilde (2E3/2)6s Rydberg State

We have determined the I P-2(3/2) and P-2(1/2) branching fractions following the photodissociation of methyl iodide (CH3I) via a number of vibronic bands associated with the (B) over tilde (E-2(3/2))6s Rydberg state at excitation wavelengths between 201.2 and 1927. nm. Vacuum ultraviolet light at 118.2 nm was used to ionize both the product iodine atoms and the methyl radical cofragments, and velocity map ion imaging was used to determine the product translational energy distribution's and angular distributions. The known relative photoionitation cross sections for (IP3/2)-P-2 and P-2(1/2) at 118.2 nm were used to determine the corresponding branching fractions. The results extend our earlier work at 193 nm by Xu et al. (J. Chem. Phys. 2013, 139, 214310), and complement the clogely related work of Gonzalez et al. (J. Chem. Phys. 2011, 135, 021102). We find that for most of the excited vibronic levels of the (B) over tilde state studied, the I P-2(3/2) branching ratio is small, but nonzero, and thatthis channel is associated with internally excited CH3 radicals. The results are discussed in relation to the recent theoretical results of Alekseyev et al. (J. Chem. Phys. 2011, 134, 044303).