Lifetimes,gFactors, and Collision Cross Sections of Hydrogen Molecules in the(1s3p)Πu3Level

Abstract

Experimental results obtained by Hanle and Bitter-Brossel effects on the $N=1\mathrm{}$ and $N=2\mathrm{}$ ($v=0, 1, 2, \mathrm{and} 3$) levels of the $\mathrm{}\left(1s3p\right)\mathrm{}{}_{}{}^3{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ state of the parahydrogen molecule excited by electron impact are presented. Resonances are found at the experimentally lowest possible frequencies (21-64 MHz) in a region where the N. S decoupling is nonexistent for the $N=2\mathrm{}$ level [the measured Landé $g$ factors are 0.77 ± 0.01 and 0.48 ± 0.02 corresponding to a pure Hund's-coupling case (b)] and just beginning for the $N=1\mathrm{}$ level (at 21 MHz the apparent measured $g$ is 1.235 ± 0.01). These results together with the calculations carried out in the case of complete N·S coupling lead to lifetimes $\tau =(3.10\mathrm{}\pm 0.3)\times {10}^{-8\mathrm{}}$ see ($N=1\mathrm{}$) and $\tau =(3.15\mathrm{}\pm 0.3)\times {10}^{-8\mathrm{}}$ sec ($N=2\mathrm{}$) and ${\mathrm{H}}_2$* - ${\mathrm{H}}_2$ cross sections $\tau =232\mathrm{}\pm 30$ ${\mathrm{\AA }}^2$ ($N=1\mathrm{}$) and $\sigma =240\mathrm{}\pm 30$ ${\mathrm{\AA }}^2$ ($N=2\mathrm{}$). The quantities $g$, $\tau$, and $\sigma$ were all found to be independent on the vibrational number. Risk of cascade was eliminated.