Sodium hydride clusters in solid hydrogen and neon: Infrared spectra and theoretical calculations

Laser-ablated sodium atom reactions with H-2 have been investigated in solid molecular hydrogens and neon. The NaH molecule and (NaH)(2,3,4) clusters were identified by IR spectra with isotopic substitution (HD and D-2) and comparison to frequencies calculated by density functional theory and the MP2 method. The use of para-hydrogen enriched samples provides evidence for a (H-2)(n)NaH subcomplex surrounded by the solid hydrogen matrix cage. The ionic rhombic (NaH)(2) dimer is characterized by strong absorptions at 761.7, 759.1, and 757.0 cm(-1), respectively, in solid neon, para-hydrogen, and normal hydrogen matrices. The cyclic sodium hydride trimer and tetramer clusters are also observed. Although the spontaneous reaction of two Li and H-2 to form (LiH)(2) occurs on annealing in solid H-2, the formation of (NaH)(2) requires near uv photoexcitation.