LIFETIME MEASUREMENTS ON PERTURBED LEVELS OF NO(B (2)PI) AND PRECISE TERM ENERGY OF THE NO(A (4)PI) STATE

Using a pulsed near-UV dye laser, the laser-induced fluorescence (LIF) excitation spectrum of the NO(B (II)-I-2 <-- X (II)-I-2) transition was measured in the (0,9) band on vibrationally hot NO in a molecular beam. Lifetime measurements were made for some of the B,v=0 and v=3 rotational/ fine structure levels, including one which was recently shown to exhibit very specific kinetic effects due to a perturbation by the NO(a (II)-I-4) state [Ch. Ottinger and A. F. Vilesov, J. Chem. Phys. 100, 1805 (1994)]. This perturbation manifested itself in the present work by g significantly longer lifetime of the (II3/2)-I-2(l0.5) level relative to other B,0 levels. The same effect was observed for the B,v= 3 (II1/2)-I-2(17,5) level. The S/O interaction matrix element is estimated to be very small (similar or equal to 10(-2)-10(-3) cm(-1). The perturbed level pairs must therefore be in very close, accidental coincidence. This was used for a precise determination of the term energy of the a (II)-I-4 state as T-0(a (II)-I-4) = 38 266.74+/-0.03 cm(-1).