Hanle-effect studies on the(5p46s)P524state of iodine

Hanle-effect measurements have been made on the $\left(5\mathrm{}{p}^{4}6s\right){}_{}{}^4{}_{}{}^{}P_{\frac{5}{2}}^{}{}_{}{}^{}$ state of iodine, which is connected to the ground state via the 1830-Å line. The atomic iodine is produced by thermal dissociation of ${\mathrm{I}}_2$, and is excited by unpolarized resonance radiation. Using the value of $g_J$ obtained by Keiss and Corliss from high-field Zeeman splittings, we find a radiative life-time of 57.9 ± 1.4 nsec (all errors quoted are 67% confidence limits). Neither coherence narrowing nor self-broadening is observed, and we place an upper limit of 200 ${\mathrm{\AA }}^2$ on the latter process. Cross sections for broadening of the Hanle effect by the rare gases are found to be (in ${\mathrm{\AA }}^2$): He: 9.8 ± 1.1; Ne: 19.5 ± 1.6; Ar: 37.6 ± 3.1; Kr: 38.7 ± 3.8; Xe: 49.2 ± 3.1. The relative values of these cross sections are seen to be in agreement with the predictions of a van der Waals interaction.