Correlated product distributions from ketene dissociation measured by dc sliced ion imaging

Journal Article · Sat Jan 07 04:00:00 EST 2006 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2137312· OSTI ID:20783203

Komissarov, Anatoly V; Minitti, Michael P; Suits, Arthur G; Hall, Gregory E ^[1]

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1. Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

Speed distributions of spectroscopically selected CO photoproducts of 308 nm ketene photodissociation have been measured by dc sliced ion imaging. Structured speed distributions are observed that match the clumps and gaps in the singlet CH{sub 2} rotational density of states. The effects of finite time gates in sliced ion imaging are important for the accurate treatment of quasicontinuous velocity distributions extending into the thickly sliced and fully projected regime, and an inversion algorithm has been implemented for the special case of isotropic fragmentation. With accurate velocity calibration and careful treatment of the velocity resolution, the new method allows us to characterize the coincident rotational state distribution of CH{sub 2} states as a smoothly varying deviation from an unbiased phase space theory (PST) limit, similar to a linear-surprisal analysis. High-energy rotational states of CH{sub 2} are underrepresented compared to PST in coincidence with all detected CO rotational states. There is no evidence for suppression of the fastest channels, as had been reported in two previous studies of this system by other techniques. The relative contributions of ground and first vibrationally excited singlet CH{sub 2} states in coincidence with selected rotational states of CO ({upsilon}=0) are well resolved and in remarkably good agreement with PST, despite large deviations from the PST rotational distributions in the CH{sub 2} fragments. At 308 nm, the singlet CH{sub 2} ({upsilon}{sub 2}=0) and ({upsilon}{sub 2}=1) channels are 2350 and 1000 cm{sup -1} above their respective thresholds. The observed vibrational branching is consistent with saturation at increasing energies of the energy-dependent suppression of rates with respect to the PST limit, attributed to a tightening variational transition state.

• OSTI ID: 20783203
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 124; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
DISSOCIATION
DISTRIBUTION
ENERGY DEPENDENCE
FRAGMENTATION
GROUND STATES
KETENES
PHASE SPACE
PHOTOLYSIS
PHOTON-MOLECULE COLLISIONS
REACTION KINETICS
ROTATIONAL STATES
VIBRATIONAL STATES