The ν₂ infrared band of 1-phosphapropyne CH₃CP

The Fourier transform infrared spectrum of 1-phosphapropyne CH₃CP has been recorded in the region 1470-1580 cm^-1 with a resolution of 0.01 cm^-1, and the ν₂ band centered at 1558.7416(28) cm^-1 was analyzed. The 689 observed transitions with J′ and K′ values up to 69 and 8, respectively, were assigned. A set of the spectroscopic constants determined for the upper v₂ = 1 state reproduced the experimental wavenumbers with an rms error of 0.0025 cm^-1. No significant perturbations were observed. The ν₂ + ν₈ - ν₈ hot band, centered at 1553.5492(35) cm^-1, was also analyzed. The upper state constants determined from the 341 observed transitions with J′ and K′ values up to 53 and 6, respectively, reproduced the experimental wavenumbers with an rms error of 0.0047 cm^-1.