Reinvestigation of the Hanle Effect for the NO A 2Σ+ State

Abstract

The coincidence of the CdII 2144.38‐Å line with the $R_1\text{(25\hspace{0.17em}/\hspace{0.17em}2)}$ and the ${}^R{Q}_{21}\text{(25\hspace{0.17em}/\hspace{0.17em}2)}$ lines of the (1, 0) band of the NO $\gamma$ system $A^2{\Sigma }^{+}{\mathrm{-X}}^2\Pi$ is used to perform a measurement of the molecular Hanle effect on the $\text{(υ′\hspace{0.17em}=\hspace{0.17em}1, N′\hspace{0.17em}=\hspace{0.17em}13)}$ vibration‐rotation level of the excited state. A linear fit to the pressure‐broadening data yields an intercept of 4.25 ± 0.3 G for the zero‐pressure linewidth and a slope of 16.3 ± 0.2 mG/mtorr. This is in disagreement with the value of 5.5 ± 0.5 G reported by Gouedard and Lehmann for the half‐width at half‐maximum. If we assume a $g$ value calculated for Hund's case (b) coupling, the radiative lifetime calculated from our half‐width at half‐maximum is in good agreement with the work of Jeunehomme. The previous results of Crosley and Zare are shown to be spurious because of mercury vapor contamination.