Laser-ablated silicon atoms react extensively with hydrogen to form the silicon hydrides SiH1,2,3,4 and the disilicon, hydrides Si2H2,4,6, Infrared spectra and density functional theory frequency calculations with HD and D-2 substitution are used to identify these species in solid neon, argon, and deuterium. The novel dibridged Si2H2 species is characterized by an antisymmetric Si-H-Si stretching mode at 1100.3 cm(-1) and the transfolded Si2H4 intermediate by antisymmetric SiH2 stretching and bending modes at 2151.6 and 858.5 cm(-1) in solid neon. The SiH3- anion is identified by photosensitive absorptions at 1856 and 1837 cm(-1) in solid neon. Silicon atoms in pure deuterium gave primarily SiD4 With some SiD3, Si2D6, and Si2D4 and no evidence for SiD and SiD2, but SiD3-and SiD2- were observed.