Photodissociation of BrCN and ICN in the a continuum: Vibrational and rotational distributions of CN(X 2Σ+)

Abstract

We report results of experiments on photodissociation of ICN and BrCN in the long-wavelength (A) continuum in which primary rotational and vibrational distributions of CN in its electronic ground state are determined. For the CN fragment from ICN, our observations at 222 and 249 nm, reported here, together with our earlier results at longer wavelengths, show that the fraction of energy which goes into rotation (in the ground-state channel) is very nearly independent of exciting wavelength in the range 222–351 nm. This holds for each of CN vibrational levels 0, 1, and 2, where the fractions are 15, 25, and 33% respectively. The vibrational distributions decrease monotonously with υ, but show little change as a function of exciting wavelength. CN distributions are also presented for the photodissociation of BrCN at 193, 222, 249, and 308 nm. Results for both parent molecules are briefly discussed in relation to other recent experimental and theoretical work.