Correlations of NO rotation and translation produced in the photofragmentation of 2-chloro-2-nitrosopropane via two dissociation channels

Correlated rotational and translational product state distributions of the NO X 2Π1/2,3/2 (v=0) product of the dissociation of 2-chloro-2-nitrosopropane in a molecular beam following à 1A″←X̃ 1A′[n(N),π*(N=0)] excitation at 600 and 650 nm are measured by resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry in a molecular beam. The NO speed distribution appears bimodal and the average speed increases with NO rotational quantum number. The slow component of the NO velocity distribution is attributed to dissociation on the S0 surface and the fast component to dissociation across a barrier along the reaction coordinate on the T1 surface. A two-channel dynamical model based on statistical phase space theory is used to model the correlated NO rotational and translational distributions. The experimental data are consistent with a C–N bond energy of 12 900±200 cm−1 on the S0 surface and a barrier height of 1500±200 cm−1 on the T1 surface. The high rotational excitation of NO products originating on the T1 surface can be attributed to impulsive recoil of NO from a bent C–N–O geometry atop the T1 barrier.