Lifetime Determination of the NO A Σ+2 State

A coincidence of the Te I emission line at 2147.25 Å with the Q₁(21/2) and the ^QP₂₁(21/2) absorption lines of the (1, 0) band of the NO γ system is used to perform a Hanle‐effect measurement on the v′=1, N′=10 level of the NO A ${}^2{\Sigma }^{+}$ state. A linear least squares fit to the pressure‐broadened data yields an intercept of $\text{3.37 ± 0.36\hspace{0.17em}}\mathrm{G}$ for the zero‐pressure linewidth and a slope of $\text{12.7 ± 2.4\hspace{0.17em}}\mathrm{mG}/\mathrm{mtorr}$ . By measuring the zero‐field polarization of the resolved fluorescence lines, the ratio of the hyperfine splitting to the rotational spin splitting is estimated to be less than or equal to 1:5, and the angular momentum coupling scheme is found to conform closely to Hund's case (b_βJ). An optical radio‐frequency double resonance study provides further confirmation. Using g values appropriate to Hund's case (b_βJ), the radiative lifetime is determined to be $\text{178 ± 19\hspace{0.17em}}\mathrm{nsec}$ . These results are in excellent agreement with the previous Hanle‐effect measurements by German, Zare, and Crosley on the v′=1, N′=13 level.