Sign of the temperature dependence of k(CH + OCS) between 58–150 K

Ascertain whether the bimolecular rate coefficient for the CH(X^2Π) + OCS gas-phase reaction exhibits a positive or negative temperature dependence in the 58–150 K range by performing additional low-temperature kinetic measurements under uniform supersonic flow conditions, thereby clarifying the trend suggested by prior higher-temperature experiments and statistical rate theory.

Background

The authors measured k(T) for CH + OCS between 32–58 K and observed no significant temperature dependence in that range. Prior work at 297–667 K reported a slight negative temperature dependence, and theory suggests a negative trend near 150 K.

Their measured low-temperature value at 32 K is consistent with a decreasing trend but does not allow them to confirm the sign of the temperature dependence between 58–150 K, motivating further experiments.

References

However, a positive or negative temperature dependence cannot be confirmed from the measurements made in this work and further experimental measurements are required from 58 K to 150 K in order to fully examine this temperature dependence.

— Design and Implementation of a New Apparatus for Astrochemistry: Kinetic Measurements of the CH + OCS Reaction and Frequency Comb Spectroscopy in a Cold Uniform Supersonic Flow (2405.18814 - Lucas et al., 29 May 2024) in Section III.D. CH + OCS Temperature-dependent Reaction Rate Coefficients