A system of HNO in the far ultra-violet and measurement of its oscillator strength

Abstract

The diffuse bands between 2080 and 1980 Å which McGrath and McGarvey ¹ assigned to CH₃O, and which Napier and Norrish ² later reassigned to nitrosoformaldehyde, have been observed in the black-body flash photolysis of NO/H₂ mixtures, and also in the Hg(6³P₁)-flash-photosensitized decomposition of H₂ containing a trace of NO. The carrier of the bands has been assigned to the HNO molecule; its rate of formation is consistent with the known rate of the reaction H + NO + H₂→HNO + H₂; the carrier is produced in a fast reaction of HgH with NO. Tests described by earlier workers to exclude the possibility that HNO is the carrier have been shown to be invalid. The oscillator strength of the strongest HNO band at 2073 Å was measured as 3(±1)× 10^–2; the total oscillator strength of the system is ∼8 × 10^–2.

Flash excitation of NOX²Π to NOA²∑⁺(ν= 0-2) in the presence of H₂. resulted in HNO formation under conditions to negligible quenching of NOA²∑⁺ by H₂. The yield of HNO was shown to be proportional to the NOA²∑⁺ quenched by NOX²Π, rather than being proportional to the total NOA²∑⁺ excited.