Potential Function for the Ring Puckering Vibration of B2H6 and B2D6

The $\text{v = 1 → 2}$ transition of the ring puckering mode of B₂H₆ has been observed at 389.5±0.5 cm⁻¹ and identified on the basis of relative intensity measurements of the rotational fine structure of the overlapped $\text{v = 0 → 1}$ and $\text{v = 1 → 2}$ bands. The band center for the ring puckering fundamental has been determined to be 369.3 cm⁻¹ utilizing an asymmetric rotor calculation. The potential function for the ring puckering vibration based on the $\text{v = 0 → 1}$ and $\text{v = 1 → 2}$ transitions is V(X) = 25.25(X⁴+11.78X²), where X is a reduced coordinate. The band centers for the $\text{v = 0 → 1}$ and $\text{v = 1 → 2}$ bands for B₂D₆ were assigned to the ``holes'' in the band envelope at 261.3 and 272.6 cm⁻¹, respectively. The rotational fine structure in the bands of the deuterated molecule was not resolved. The potential for the deuterated molecule predicted from a reduced mass model is V(X) = 15.93(X⁴+14.71X²).