The rotation-vibrational Raman spectrum of the v11 fundamental band of allene has been recorded. The spectrum consists of a series of Q-branches and partly resolved J-structure in the subbands. The Q-branches in one component of the hot band 2v11-vll have been identified. The following constants have been obtained: vo = 352.73 & 0.05 cm-l, AO = 4.81 1 + 0.003 cm-l, (11 = 0.816 + + 0.001, AA = -0.0129 :k 0.0003 cm-l, AB = (4.7 f 0.6) x cm-1. An I-type doubling is observed and the I-type doubling constant q&' is estimated as -(2.7 & + 0.8) x cm-1. The analysis of the Raman spectrum shows that the assignment of the Q-branch maxima in the infrared spectrum of v11[4, 51 has to be changed by two units. cm-l and DK = (2.4 & 0.1) x The Raman spectrum of vll obtained in the present work shows unresolved Qbranches and partly resolved J-structure in the 0-, P-, Rand S-branches of the subbands. AB and an I-type doubling constant were determined directly and, by combination with the infrared measurements [4, 51, the constants v,, A. and ill were calculated. The uncertainty in the determination of the band centre of the infrared Journal of Raman Spectroscopy 2 (1974) 31-52. All Rights Reserved Copyright 0 1974 by D . Reidel Publishing Company, Dordrecht-Holland 32 FLEMMING HEGELUND ET AL.spectrum of vI1 discussed in [5] has been removed and the assignment of the Qbranches proposed in [4] has been changed by two units. Finally, a series of Q-branches due to a component of the hot band 2v1,-v,, has been identified and an assignment is proposed using intensity considerations. ExperimentalThe 200-500cm-' region of the Raman spectrum of vll has been obtained using the instrument described by Brodersen and Bendtsen [7]. The sample of allene was

Many of the fundamental bands of aUene-d4 have been analysed to yield a number of molecular constants, including the ground state constants A. -Bo = 2.1832 f 0.0004 cm-' and Dm, = (2.8 f 0.2) x cm-'. A reassignment of the perpendicular bands u, and ull is proposed.