HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: V. ROTATIONAL SPECTRA OF ALLENE, ALLENE-d4, AND ALLENE-1,1-d2

The pure rotational Raman spectra of allene, allene-d 4 and allene-1,1-d 2 were photographed in the second order of a 21 ft. grating. Two plates of each spectrum were analyzed yielding the following values for the rotational constants:[Formula: see text]These constants lead to the value r 0 (C=C) = 1.308 8 ± 0.001 Å. Also if a value of r 0 (C—H) = 1.07 ± 0.01 Å is assumed, then [Formula: see text]. It is noted that the length of the carbon–carbon double bond in allene is significantly shorter than that in ethylene.