Knowledge Bank

The infrared vibration-rotation spectrum of $D2CO$ vapor has been measured in the region from 1200 to $700cm-1$ with resolution of about $0.07cm-1$. Three bending bends $\nu 3,\nu 6$, and $\nu 4$ have been resolved and assigned by use of the Loomis-Wood diagrams and the ASSIGN $diagrams.1$ The levels with $Ka\prime =0-8$ (for $\nu 3$), $Ka \prime =0-15$ (for $\nu 6)$ and $Ka\prime =0-14$ (for $\nu 4)$ are assigned. Besides the strong a-type Coriolis interaction between $\nu 6$ and $\nu 4$, a c-type Coriolis interaction between $\nu 3$ and $\nu 6$ and a b-type Coriolis interaction between $\nu 3$ and $\nu 4$ are observed. By a least-squares fit in the scheme of three-level Coriolis interactions, the molecular constants for the $\nu 3,\nu 6$, and $\nu 4$ states were determined: $\nu 3=1100.44 cm-1,\nu 6=989.19 cm-1,\nu 4=938.02 cm-1,\xi 64a=4.98 cm-1,\xi 36c=0.68 cm-1$, etc. The perturbed intensity distribution of the three bands is best simulated with the relative band moment of $(-0.4:1.0:0.5)$ for $\nu_{3}: \nu_{6}: \nu_{4}).