Intensity distribution in pure rotational Raman spectra of linear molecules in the ground and vibrational II states application to acetylene

The pure rotational Raman spectrum of acetylene has been recorded with argon laser excitation and a resolution of about 0.3 cm −1 . For the first time ΔJ = 1 transitions in the excited II states are clearly resolved up to J = 9. Formulae for the intensity distribution in rotational Raman spectra of linear molecules in the ground and vibrational II states have been derived including the effect of I ‐type doubling. After a qualitative discussion these formulae are applied to a quantitative analysis of the acetylene spectrum.