Knowledge Bank

An examination of previous work on the allene molecule indicated that a complete re-examination of the rotation-vibration spectrum with high dispersion would be of value in obtaining more satisfactory vibrational assignments, $\zeta$ factors, and force constants. Consequently, a systematic attempt has been made to resolve the parallel bands in the regions 7.1$\mu$, 5.1$\mu$, and 3.3$\mu$ and the perpendicular bands in the regions 3.2$\mu$ and 8-14$\mu$. In particular, the perpendicular band at about 4.1$\mu$ which was incompletely resolved by Lord and $Venkateswarlu1$ has been examined with a 7500-lines-per-inch grating using longer absorbing paths and has been satisfactorily resolved. During the course of this work there was published a paper by Overend and $Thompson2$ in which they resolved two parallel bands, the one at 3.3$\mu$ more clearly than the other. The present work is in agreement with these new published data. A discussion of all the presently available data with reference to the molecular structure of allene will be presented.