Knowledge Bank

Extensive diode laser spectra of $H2D+$ in the $2000-2500cm-1$ region and of $D2H+$ in the $1800-2300cm-1$ region have been recorded. These data are supplemented by difference-frequency laser measurements on $H2D+$ by Crofton and Oka, and by ion beam measurements on $D2H+$ by Shy and $Wing.1$ For both isotopes the $\nu 2$ and $\nu 3$ vibrations are strongly coupled by a Coriolis interaction, and the bands must be analyzed simultaneously; these analyses have now been accomplished. Previous $studies2$ of the $\nu 1$ bands were very helpful in providing ground state combination differences to confirm our assignments. For $H2D+$, over 60 transitions have been assigned and fitted with a standard deviation of about $0.008cm-1$, and for $D2H+$ the numbers are similar. The resulting molecular parameters are in good general agreement with ab initio $calculations.3$