Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations

Abstract

A combined experimental and theoretical study of quantum state-resolved rotational energy transfer kinetics of optically centrifuged CO molecules is presented. In the experiments, inverted rotational distributions of CO in rotational...

Transient IR spectroscopy of optically centrifuged CO2 (R186–R282) and collision dynamics for the J = 244–282 states

“…In a related study on CO(J) relaxation, however, we used master equation simulations to calculate the relaxation kinetics and rotational distributions of optically centrifuged CO with J # 80, based on extrapolated rate constants from state-to-state measurements for J = 0-29. 27,28 The simulations successfully reproduced the qualitative features of the experimental results, with the key exception that the calculated relaxation rate constants were 5 times larger than those measured in the experiments. The statistical model for the CO system considered the increasing energy gaps for high J states, but the effects of large angular momentum and short rotational periods were not included.…”

Investigation of Methylcyclopentadiene Reactivity: Abstraction Reactions and Methylcyclopentadienyl Radical Unimolecular Decomposition

“…It is in fact known that the proper theoretical description of collisional energy transfer requires a model where the energy transferred by each collision is a function of both energy ( E ) and momentum ( J ). While it is sometimes possible to effectively describe the energy transfer with a 1D model using an efficient energy transfer parameter, which may be evaluated for example over the results of trajectory simulations as suggested by Jasper, it is also known that in some cases this approach may fail . In this light, this reaction channel may prove to be an interesting reference system for the development of energy transfer models that are more theoretically consistent than the single-exponential down model used in this work .…”

“…While it is sometimes possible to effectively describe the energy transfer with a 1D model using an efficient energy transfer parameter, which may be evaluated for example over the results of trajectory simulations as suggested by Jasper, 41 it is also known that in some cases this approach may fail. 57 In this light, this reaction channel may prove to be an interesting reference system for the development of energy transfer models that are more theoretically consistent than the single-exponential down model used in this work. 58 The main product of the C 6 H 6 + H reaction is the cyclohexadienyl radical (W6) up to about 1500 K. Above this temperature, conversion to fulvene and stabilization of W3 become competitive, with conversion to fulvene becoming the major channel as the pressure decreases.…”

Mixed quantum/classical calculations of rotationally inelastic scattering in the CO + CO system: a comparison with fully quantum results

“…For weaker transitions and lower collision energies the cross sections predicted by MQCT may be a factor of 2-3 different from those obtained by full-quantum calculations for CO + CO. Although there was a significant recent interest in the experimental studies of CO rotational excitations, 22,49 there are no direct experimental measurements of absolute values of inelastic cross sections or rate coefficients for the rotational state-to-state transitions in CO + CO collisions, to the best of our knowledge. We hope that this theoretical work will stimulate new experimental efforts.…”