Photofragmentation of Ketene to CH2(3B1) + CO. 2. Rotational-State Distribution of Product CO

DOI: 10.1021/j100364a044

Source and publish data:

Journal of Physical Chemistry p. 269 - 274 (1990)

Update date:2022-08-12

Topics:

Authors:

Chen, I-Chia

Moore, C. Bradley

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Article abstract of DOI:10.1021/j100364a044

Ketene ccooled in a supersonic jet is photolyzed at 1120, 190, and 30 cm^-1 above and 50 cm^-1 below the top of the barrier to dissociation on the triplet surface.The barrier is 1330 cm^-1 above CH2(<*>3B1) + CO.The rotational-state distributions of CO produced from triplet ketene are measured by vacuum-UV laser-induced fluorescence.These distributions cannot be described adequately by a Boltzmann temperature or by phase space statistical models.An average of 22.4 +/- 1percent of the total available energy goes to CO rotation as predicted by an impulsive model using the ab initio transition-state geometry.This indicates that the energy partitioning is determined by the geometry of the transition state with the repulsive force directed along the breaking bond.The fraction of energy going to CO rotation does not depend on the photolysis wavelenght.The Gaussian shape of the CO rotational-state distribution can be understood quantitatively in terms of zero-point motion of the C-C-O bending vibration of the transition state.Even when the excess energy above the top of the barrier is comparable to the barrier height itself, the energy release appears to be completely dynamically controlled.