Vibration-rotation bands of allene-1 . 1- d 2

Abstract
The spectrum of allene-1 . 1- d 2 in the range 3 to 20 μ has been measured using high resolving power. An analysis of several parallel-type bands has given values for B 0 which agree closely with that obtained from the rotational Raman spectrum (0∙2619 cm –1 ). In assigning the perpendicular bands to particular vibrations, some characteristic details of their rotational structure arising from the slight asymmetry have been taken into account. From a rotational analysis of four perpendicular bands it has been possible to derive a value for ( A 0 ─ B 0 ), from which A 0 is obtained. Using B 0 values for allene, allene- d 2 and allene- d 4 , and the new value for A 0 of allene- d 2 , the geometrical parameters have been calculated, namely, r 0 CH = 1∙080 Å, r 0 cc = 1∙308 Å, and ∠HCH = 119°. Some of the perpendicular bands at longer wavelengths illustrate a special type of Coriolis interaction between B 1 and B 2 class vibrations, and the results are in general accord with Nielsen’s theory of this effect.
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