The NO(a(4)Pi) state: Collisional removal of v=11 and a4 Pi-B-2 Pi interactions

Vibrationally excited levels of the a (4) Pi state, the lowest electronically excited state of the NO molecule, can be studied through their collisional energy transfer to the radiating B (2) Pi state. Following one-photon excitation in the 11-O band of the forbidden a (4) Pi-X 2 Pi: transition with the output of a tunable dye laser, we monitor the temporal evolution of the emission from the v=2 level of the B (2) Pi state. From pressure-dependence analysis, we determine the removal rate coefficients fora (4) Pi(v=11) with NO, O-2, N2O, N-2, CO2, He, and Ar. In addition, using direct B 2 Pi excitation of the v=2,3,4 levels, we obtain removal rate coefficients for the same colliders. These vibrational levels span the region around a (4) Pi(v=11). In general, a (4) Pi removal is quite fast, ranging from rate coefficients of 1.0x10(-12) cm(3) S-1 to more than 1.0x10(-10) cm(3) s(-1), and is substantially faster than B (2) Pi removal for N-2, N2O, CO2, and Ar. NO(B (2) Pi, v=3) removal is generally much faster than that for the v=2 and v=4 levels, because of a localized perturbation between the v=12 level of the a (4) Pi state and v=3 of the B (2) Pi state. Preliminary measurements on transfer between the b (4) Sigma(-) and B (2) Pi states are reported. (C) 1997 American Institute of Physics.