TOTAL AND STATE-TO-STATE RATE COEFFICIENTS FOR ROTATIONAL ENERGY-TRANSFER IN COLLISIONS BETWEEN NO(CHI(2)PI) AND HE AT TEMPERATURES DOWN TO15 K

Infrared-ultraviolet double resonance (IRUVDR) experiments have been i mplemented in the ultra-cold environment provided by a CRESU (Cinetiqu e de Reaction en Ecoulement Supersonique Uniforme) apparatus. This has enabled us to measure rate coefficients for rotational energy transfe r in collisions between NO and He of two kinds: those relating to tota l removal from a specific rovibrational state of NO(X (2) Pi; Omega = 1/2; upsilon = 3; J = 0.5, 3.5 or 6.5) and also state-to-state rate co efficients for transfer from these levels. Using different Laval nozzl es, results have been obtained at four different temperatures: 149, 63 , 27 and 15 K, and are also reported for 795 K. (C) 1997 Elsevier Scie nce B.V.