AbstractThe 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 toJ= 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 ofI‐type doubling. After a qualitative discussion these formulae are applied to a quantitative analysis of the acetylene spec