State specific electronic quenching rates for 14N+2 and 15N+2

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Abstract
We have conducted laser double resonance experiments to measure the branching ratio for the rates of electronic transfer from the A 2Πui (v=4) state to the X 2∑+g (v=8 and 7) levels for 14N+2 and 15N+2. Because of the propensity for ΔJ∼0 in these electronic transfer processes, the energy gaps can be determined and although they are similar in magnitude for the two isotopes, the branching ratios are significantly different. For 14N+2 the rate from A(v=4) to X(v=8) is about twice as great as to the X(v=7) level whereas for 15N+2, this ratio is approximately 6. This difference is reflected in the dramatic change in shape from 14N+2 to 15N+2 of the radiative decay curve from the A 2Πui (v=4) level. The 14N+2 curve appears to be single exponential in contrast to the double exponential for 15N+2. We use these branching ratios in an electronic relaxation model that describes the observed decay curves well, to deduce the state specific electronic quenching rates for these two isotopes.