A re-evaluation of the effects of parent-molecule bending and overall rotation in triatomic direct photofragmentation. A more extensive study of ICN + hv → CN + I

Abstract

The classical trajectory method has been used to investigate product energy partitionings in the 234–266 nm photolysis of ICN. The calculations, which include effects of ICN bending and overall rotation, consider ICN prior to photon absorption in the (0, 0 0 , 0) ground vibrational state and with a rotational angular momentum appropriate to the most probable ICN rotational state ( j mp = 32) at 300 K. Model potentials employed closely approximate those introduced by Morse, Freed and Band, and permit photodissociation to form both ground state I( 2 P 3 2 ) and excited state I( 2 P 1 2 ). Description of the ICN(0, 0 0 , 0) vibrational phase-space distribution prior to photolysis is given either by the Wigner distribution function or by the classical (300 K) distribution function. Results obtained indicate that for the model potentials employed, photolysis to form I( 2 P 3 2 ) produces relatively cold CN rotational distributions (for individual CN vibrational states) and that the fraction of available product energy entering CN rotation is insensitive to photolysis wavelength. For I( 2 P 1 2 ) formation, CN rotational excitation increases markedly with decreasing photolysis wavelength (increasing photon energy). In contrast to the findings of an earlier preliminary study, present results indicate that use of a collinear, rotationless approximation is often successful in describing the CN vibrational state distribution following ICN photodissociation.