The direct photolysis of silane at 1470 Å results in the production of hydrogen and disilane. By photolyzing equimolar mixtures of silane and perdeuterosilane and studying the isotopic distribution of the products, a silene insertion chain mechanism is proposed: SiH₂* + SiH₄ → Si₂H₆ Si₂H₆ → SiH₂** + SiH₄* SiH₄* → SiH₂** + SiH₄ → Si₂H₆. The source of the initial silene species is uncertain: the initial elimination of molecular hydrogen SiH₄ → SiH₂ + SiH₄ → H₂ is favored but some silyl formation followed by disproportionation cannot be ruled out. The deposition of a silicon containing film on the lamp window during photolysis made accurate measurement of quantum yields impossible.
