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Formation, reactions and spectra of some group V free-radicals Yee, Kim Kuo

Abstract

Metastable, electronically excited atoms (²Dº , ²Pº ) of phosphorus, arsenic and antimony have been observed following the isothermal flash photolysis of Group VA hydrides and trihalides. Several mechanisms for the production of these atoms are discussed. The decay of the excited atoms was observed to be rapid due to reactions with the transients produced in the flash photolysis of the parent compounds. Flash photolysis of the Group VA hydrides and trichlorides has yielded new electronic absorption spectra of the AsH and AsH₂, SbH and SbH₂, PC1, AsC1, and SbC1 free-radicals. Vibrational analysis on some of these spectra have been carried out. In the isothermal flash photolysis of cyanogen with Group VA hydrides, it is proposed that the following reactions of the cyanogen radical occur rapidly: CN + AH₃ → AH₂ + HCN (1) CN + AH₂ → AH + HCN (2) CN + AH → ACN + H (A=N,P,As) (3) → HCN + A* (A=P,As, Sb) (4) (formula omitted) HACN (A=N,P) (5) where A, unless specified, is N, P, As or Sb and * denotes electronic excitation. Three of the new electronic absorption spectra observed are tentatively attributed to the PCN, HPCN and AsCN free-radicals produced in reactions (3) and (5). The assignment of the other spectra is discussed. Reactions of CN with NF, PC1 and AsC1, corresponding to (3), have also been shown to occur rapidly. The reactions of the cyanogen radical in the flash photolysis of cyanogen with nitrous oxide, oxygen, water, and methyl isocyanate have also been studied and discussed.

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