The infrared spectrum of diazirine: . Rovibrational analysis of the ν3 fundamental

Diazirine is one of the seven possible isomers of diazomethane. The medium-resolution infrared spectrum of this cyclic compound, which seems to be very stable in the gas phase, was reported by Ettinger. The mid-infrared spectra of diazirine and of the substituted isotopic species D₂CN₂, H₂¹³CN₂, and H₂C¹⁵N₂ were recorded with a resolution of 0.08 cm^?1. The overall assignment of these spectra is reported here. The ν₃ fundamental of the main species at 1459.15 cm^?1 (CH₂ deformation) is an A-type parallel band but presents a complicated band structure since diazirine is an asymmetric rotor with κ = ?0.427. The rovibrational assignment and the analysis of this band, together with the determination of the molecular constants, is given.