Infrared Spectrum of Acetylene-d1

Abstract

The high‐resolution absorption spectrum of C₂HD has been studied in the 1900 to 3400 cm^—1 region. Several bands at lower frequencies have been examined with medium resolution. Nineteen bands were analyzed for their rotational constants. Combination differences of four transitions from the ground state were averaged and the rotational constants B₀=0.99156±0.00004 cm^—1 and D₀=1.17±0.07×10^—6 cm^—1 obtained. This B₀ value together with those recently obtained for C₂H₂ and C₂D₂ have been used to calculate the ground‐state and equilibrium bond distances of the acetylene molecule. The l‐doubling constants for the degenerate modes were determined to be q₄=4.4₂×10^—3 cm^—1 and q₅=3.₆×10^—3 cm^—1. The frequencies of the bending modes have been calculated by use of difference bands to be ν₄¹=518.38 cm^—1 and ν₅¹=677.77 cm^—1.