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.