MICROWAVE-SPECTRA OF ALKALI-METAL TETRAHYDROBORATES IN EXCITED VIBRATIONAL-STATES

We have observed two sets of vibrational satellites for each of LiBH4, NaBH4, NaBD4, and KBH4 and have assigned them to the non-degenerate alkali metal-boron stretching state and the degenerate BH4 bending (or internal rotation) state. The observed spectral patterns were found to be quite different for different molecular species. The most conspicuous anomaly was the DJK constant of NaBH4, which was opposite in sign for the two vibrational states and was accounted for by accidental degeneracy of the two states strongly coupled by a Coriolis interaction. © 1992.