Knowledge Bank

The spectrum of allene-$d4$ between 1880 and $2390cm-1$ was measured on a Bomem high resolution Fourier transform spectrometer and deconvolved to a linewidth of $0.0025-0.0028cm-1$. The main bands in this region include the $C=C$ stretching fundamental $\nu 6$ (species $B2$) and the two C-D stretching fundamentals $\nu 5(B2)$,and $\nu 6$(E), accompanied by the $\nu 2+\nu 7(B2)$ combination band enhanced by Fermi resonance with $\nu 5$. All the bands exhibit severe perturbations by numerous combination and overtone levels. The interacting states deemed responsible for the stronger perturbations were incorporated in the Hamiltonian and a rovibrational analysis of the observed spectrum was carried out with the aid of our computer program system SYMTOP. A much improved set of spectroscopic constants will be reported for the upper states of the fundamental bands and for some of the porturbing states. An accurate set of ground state constants will also be given.