Knowledge Bank

Earlier microwave studies have shown malonaldehyde to exist in an intramolecular enolic hydrogen bonded form with a low lying state $(16\pm 14 cm-1)$ indicating a symmetric double minimum $potential.1,2$ We have analyzed perturbations from a rigid rotor arising from Coriolis interactions between the ground state and the low lying state for several isotopic species in which deuterium has been substituted into the hydrogen bond. For the dideuterated species, the energy spacing was found to be $86448.12\pm$ 0.53 MHz, and direct transitions between the two states have been observed. For the O-d monodeuterated species, the energy spacing was $87402\pm$ 131 MHz and for the dideuterated doubly substituted $O18$ species, the energy spacing $81405\pm$ 58 MHz. The implications of these results with respect to the potential function will be discussed and comparisons with theoretical calculations will be made. Progress on the analysis of perturbations at higher J levels for the normal species will be reported.