Full State-Resolved Energy Gain Profiles of CO2 from Collisions with Highly Vibrationally Excited Molecules. II. Energy-Dependent Pyrazine (E = 32 700 and 37 900 cm–1) Relaxation

Abstract

The full state-resolved distribution of scattered CO2 (00(0)0) molecules from collisions with highly vibrationally excited pyrazine (E = 32,700 cm(-1)) is reported and compared to previous studies on pyrazine (E = 37,900 cm(-1)) to investigate how internal energy content impacts the dynamics for collisional quenching of high energy molecules [J. Phys. Chem. A 2010, 113, 1569]. Nascent rotational and translational energy profiles for scattered CO2 (00(0)0) molecules with J = 2-72 were measured using high-resolution transient infrared absorption and combined with earlier results for the J = 56-78 states [J. Chem. Phys. 1999, 111, 7373]. The product translational energy for individual J-states increases by 50% for a 16% increase in donor vibrational energy. The nascent rotational distribution for scattered CO2 is biexponential, comprising 77% nearly elastic collisions and 23% inelastic collisions. The spread of the rotational distribution is sensitive to donor energy, but the branching ratio for elastic and inelastic collisions is the same for both donor energies. The measured collision rates are close to the Lennard-Jones values and are only weakly dependent on changes in donor energy. The nascent energy gain distribution function P(ΔE) depends strongly on the energy, and this energy dependence is stronger than the linear dependence seen in multicollision energy transfer studies for pyrazine(E) + CO2 collisions.