NO(B-PI-2) RADIATIVE LIFETIMES - V=0-6

The zero-pressure radiative lifetime of the NO(B 2Π) state has been measured over the vibrational level range v = 0-6. Laser-induced fluorescence was the technique chosen for this study, using two different sources of ground state NO. In one case, photodissociation of NO2 at 193 nm was used to obtain a range of ground state vibrational levels, from which selected rotational levels were then pumped to the B 2Π state, while in the second case, NO in v = 0 was directly pumped. The two methods of preparing the excited state gave identical lifetime results. The data show a linearly decreasing lifetime with increasing vibrational level and to a good approximation the lifetimes, are given by τ(μs) = 2.00-0.193v. Recent calculations for the B-X system show excellent agreement with experiment at low v, and an increasing discrepancy with increasing vibrational level, the experimental lifetimes decreasing more rapidly than the calculated ones. The lifetime values fall within the 0.85-2.0 μs range for v = 0-6, and are substantially different from the 2-3 μs values that are currently quoted. Comparison of the new values with data derived from absorption studies shows good agreement even for the high vibrational levels. Absolute Einstein A factors are presented for the v′ = 6 progression. © 1990 American Institute of Physics.