Quantum state-resolved energy redistribution of highly vibrationally excited CsH(D) by collisions with H2(D2)

CsH(D) was generated in the reaction of Cs(7P) and H-2(D-2). Highly vibrationally excited CsH(D)[X-1 Sigma(+), v ''] is prepared using DSHR excitation. Then the quenching of excited CsH(D) through collisions with H-2(D-2) is investigated. Laser induced fluorescence is used to detect collisionally relaxed CsH(D). A kinetic model describes rates for quenching of excited CsH(D) at early times. Single rate coefficient measurements are unlikely to capture the complex nature of processes that generally are multistage with different relaxation rates characterizing each different stage. These distinct stages reflect the dominance of specific energy transfer mechanisms, 8-1 vibration to vibration (V-V) energy transfer process is very rapid and 1-2 vibration to rotation (V-R) energy transfer is relatively slow. Near resonant V-V exchange is a dominant early feature in ensemble evolution but energy differences in the key vibration and rotation quanta load to V-V energy defects that are compensated for by the low energy modes. This results in much more rapid ensemble equilibration. (C) 2015 Elsevier B.V. All rights reserved.