Raman spectra of asymmetric top molecules. Part 2.—ΔK=± 2 transitions in the rotational spectrum of butadiene

Abstract

ΔK= 2 transitions have been observed in the pure rotational Raman spectrum of butadiene. Rotational constants were determined for the ground state, ν₁₃ torsional mode, ν₂₄ bending mode and the 2ν₁₃ torsional state. Evidence of a Coriolis interaction between ν₁₃ and ν₂₄ was found and the rotational constants derived from those two states were corrected for this specific interaction. A–B values obtained for the four states were 1.247 82 ± 0.000 09 cm^–1, 1.226 70 ± 0.000 24 cm^–1, 1.2703 ± 0.0010 cm^–1 and 1.167 ± 0.002 cm^–1 for the ground, ν₁₃, ν₂₄ and 2v₁₃ vibrational states respectively. In addition D_K distortion constants of (3.61 ± 0.18)× 10^–6 cm^–1 and (2.6 ± 0.5)× 10^–6 cm^–1 were determined for the ground and ν₁₃ states respectively.