Journal of Chemical Physics, Vol.105, No.22, 9847-9858, 1996
No Mu-V-J Correlations in the Photofragmentation of 2-Chloro-2-Nitrosopropane
The trajectory of NO X (2) Pi(Omega = 1/2,3/2)(v = 0) produced after excitation of 2-chloro-2-nitrosopropane S-1 (A) over tilde (1)A " is studied by polarized 1+1’ resonance-enhanced multiphoton ionization with time-of-flight mass spectrometry detection, The correlations among the NO velocity v, angular momentum j, and the S-1 (A) over tilde (1)A " <-- S-0 (X) over tilde (1)A’ [n(N),pi*(N=O)] transition dipole mu of the parent molecule are measured. The dissociation occurs by internal conversion to the ground So state or intersystem crossing to the T-1 (a) over tilde (3)A " state and the observed speed distribution of the NO fragments is bimodal. There is no evidence for mu-v-j correlations for the products associated with the slow component of the speed distribution. For the higher speed component, the v-j correlation is a function of the NO rotational state, j, and is described by the bipolar moment beta(0)(0)(22). The average value of beta(0)(0)(22) is -0.17(+/-0.02) at j approximate to 11.5-22.5, more than five times larger than predicted by statistical phase space theory for dissociation on the S-0 (X) over tilde (1)A’ surface, indicating a moderate preference for a perpendicular orientation of the NO rotational angular momentum and velocity vectors. The v and j vectors are nearly uncorrelated for low NO rotational states (j less than or equal to 6.5).). The pr-v correlation described by the beta(0)(2)(20) bipolar moment does not change with j and its average value is -0.04(+/-0.01) at j approximate to 12.5-19.5. The average value of the beta(0)(2)(02) bipolar moment describing mu-j correlation is 0.04(+/-0.02) at j approximate to 7.5-24.5. These results are consistent with a mechanism involving both impulsive force due to a barrier along the reaction coordinate on the T-1 (a) over tilde (3)A " surface and forces resulting from the C-N-O bending and NO torsion about the C-N bond.
Keywords:LASER-INDUCED FLUORESCENCE;ENHANCED MULTIPHOTON IONIZATION;PRODUCT STATE DISTRIBUTIONS;VECTOR CORRELATIONS;PHOTODISSOCIATION DYNAMICS;ANGULAR-MOMENTUM;DISSOCIATION DYNAMICS;VELOCITY DISTRIBUTION;INELASTIC-SCATTERING;ROTATIONAL ALIGNMENT