Reactions of laser-ablated Ga atoms and normal hydrogen during co-deposition at 3.5 K give GaH as the major product and GaH2, GaH3, GaH2-, GaH4-, and Ga2H2 as minor products. Identifications are based on infrared spectra, isotopic substitution (D-2, H-2 + D-2 mixtures, HD), comparisons to earlier work, and frequencies calculated by density functional theory. Mercury arc radiation destroyed the GaH2- and GaH4- anions, decreased GaH and increased GaH3, destroyed Ga2H2, and produced new bands due to Ga2H4, two Ga2H5 radical isomers, and Ga2H6. ArF laser irradiation at 193 nm was particularly effective in converting GaH to GaH3 and to Ga2H6. The GaH4- anion absorptions in solid hydrogen are compatible with solid NaGaH4 bands: Near-ultraviolet excitation of GaD2- with D-2 present increases GaD4- absorptions. Warming these samples to remove the H-2 matrix replaced sharp gallium hydride molecular absorptions with broad 1800-2000, 1300-1700, and 600-700 cm(-1) bands due to higher oligomers containing terminal and bridged Ga-H bonds.