Infrared Spectra of H2 Molecules Near H Atoms Trapped in Solid H2

Laser-ablation irradiation of normal hydrogen during condensation at 3.8 K produces new IR absorptions in p -H 2 and o -H 2 cage molecules at 4151.8 and 4143.4 cm -1 that are redshifted 1.0 and 3.3 cm -1, respectively, from induced IR absorptions for each nuclear spin isomer in solid n -H 2 . Assignment to perturbed p -H 2 and o -H 2 molecules, respectively, are confirmed by experiments with p -H 2 -enriched samples. Deuterium experiments give rise to analogous bands for o -D 2 and p -D 2 at 2985.2 and 2982.4 cm -1, respectively, that are redshifted 1.6 and 2.2 cm -1 from the absorptions induced for each nuclear spin isomer in solid n -D 2 . However, investigations with solid HD give a single, sharp new line at 3621.7 cm -1, redshifted by 3.0 cm -1 from the sharp induced solid HD absorption. Comparable intensity half-lives recently observed for H atom electron spin resonance signals in solid H 2 suggest trapped H atoms as the origin of substantial induced IR intensity in adjacent H 2 molecules in the solid. The H atom−H 2 molecule interaction is stronger for o -H 2 than for p -H 2 owing to anisotopic charge distribution for o -H 2 that is lacking in p -H 2 .