Photofragmentation of ketene to CH sub 2 ( tilde X sup 3 B sub 1 ) + CO. 2. Rotational-state distributions of product CO

Journal Article · Thu Jan 11 04:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100364a044· OSTI ID:6946958

Chen, Ichia; Moore, C B ^[1]

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1. Lawrence Berkeley Lab., CA (USA)

Ketene cooled in a supersonic jet is photolyzed at 1,120, 190, and 30 cm{sup {minus}1} above and at 50 cm{sup {minus}1} below the top of the barrier to dissociation on the triplet surface. The barrier is 1,330 cm{sup {minus}1} above CH{sub 2}({tilde X}{sup 3}B{sub 1}) + 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 {plus minus} 1% 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 wavelength. The Gaussian shape of the CO rotational-state distribution can be understood quantitatively in terms of the 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.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6946958
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:1; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
CALCULATION METHODS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
DATA ANALYSIS
DECOMPOSITION
DISTRIBUTION
EMISSION SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
FLUORESCENCE SPECTROSCOPY
INFORMATION
KETENES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
ROTATIONAL STATES
SPECTROSCOPY