Lifetimes, g factors, and collision cross sections of hydrogen molecules in the (1s3p)3PI/sub u/ level

Experimental results obtained by Hanle and Bitter-Brossel effects on the N=1 and N=2 (v=0, 1, 2, and 3) levels of the $(1s3p{)}^3{\Pi }_u$ 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 level [the measured Land\'e 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 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 τ=(3.10±0.3)×10⁻⁸ see (N=1) and τ=(3.15±0.3)×10⁻⁸ sec (N=2) and H₂* - H₂ cross sections τ=232±30 Ų (N=1) and σ=240±30 Ų (N=2). The quantities g, τ, and σ were all found to be independent on the vibrational number. Risk of cascade was eliminated.