Lifetimes, g Factors, and Collision Cross Sections of Hydrogen Molecules in the (1s3p)3Πu Level

International audienceExperimental 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)3Πu 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 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 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 Å2 (N=1) and σ=240+/-30 Å2 (N=2). The quantities g, τ, and σ were all found to be independent on the vibrational number. Risk of cascade was eliminated