State-to-state rate coefficients for transfer from the rotational levels J=7.5, 20.5, 31.5 and 40.5 in NO(X (2)Pi(1/2), v=2) in collisions with He, Ar and N-2 and for J=7.5, 20.5 and 31.5 in collisions with NO: comparisons between experiment and theory

Using the infrared-ultraviolet double resonance (IRUVDR) technique, state-t o-state rate coefficients have been measured for the transfer of NO from th e initial rovibronic levels (X (2)Pi(1/2), upsilon = 2 , J(i) = 7.5, 20.5 a nd 31.5) in collisions with He, Ar, N-2 and NO itself. For relaxation by He , Ar and N-2 from the rotational level J(i) = 40.5, rate coefficients were measured by a new method in which IRUVDR was implemented instantly on NO mo lecules formed by photodissociation of NO2 at 355 nm. As J(i) is increased the distribution of states (J(f)) was found to change in two ways: (a) the distribution of Delta J(= J(f) - J(i)) values becomes narrower, and (b) neg ative values of Delta J are increasingly favoured over positive values. Thu s > 80% of the transfer from J(i) = 40.5 is to J(f) = 39.5. As with the ear lier experimental results for total transfer, the present results for NO-He and NO-Ar collisions are shown to agree quite well with those from coupled states quantum scattering calculations on ab initio potential energy surfa ces, although the agreement becomes poorer at high J(i). Possible reasons f or this discrepancy are discussed.