Dynamics of the photodissociation of triplet ketene

Journal Article · Fri Mar 01 04:00:00 EST 1996 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.471059· OSTI ID:285350

Gezelter, J D; Miller, W H ^[1]

---

1. Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

Calculations of the microcanonical dissociation rate for vibrationally excited ketene on the first excited triplet surface ({ital T}{sub 1}) are presented. The calculations utilize the quantum reactive scattering methodology of absorbing boundary conditions (ABC) with a discrete variable representation (DVR) to obtain the cumulative reaction probability for dissociation over the barrier. Model 1- and 2-degree of freedom potential energy surfaces for the {ital T}{sub 1} surface were obtained by fitting to the best available {ital ab} {ital initio} structures, energies, and frequencies. The dissociation rates in these reduced-dimensionality calculations give good overall agreement with the experimentally measured rates, although the steplike features seen in the experiments are washed out by the tunneling through the narrow barrier predicted in the {ital ab} {ital initio} calculations. Further model calculations reveal that a barrier frequency of approximately 50{endash}100{ital i} cm{sup {minus}1} is required to recover the step structure seen experimentally, which suggests that there is either another transition state region on the {ital T}{sub 1} surface farther out towards the product channel, or that there is surface-hopping dynamics taking place between the {ital T}{sub 1} and {ital S}{sub 0} ketene potential energy surfaces, or that the {ital ab} {ital initio} barrier frequency is simply too large. {copyright} {ital 1996 American Institute of Physics.}

• Research Organization: Lawrence Berkeley National Laboratory
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 285350
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 104; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
DEGREES OF FREEDOM
DISSOCIATION
ENERGY-LEVEL DENSITY
FINE STRUCTURE
KETENES
PHOTODISSOCIATION
PHOTOLYSIS
POTENTIAL ENERGY SURFACES
REACTION RATES
TRIPLETS