FOURIER-TRANSFORM INFRARED-SPECTROSCOPY OF THE BH3 NU-3 BAND

The gas-phase infrared spectrum of the BH3 nu(3) band was observed in the 2600 cm-1 region by a Fourier transform infrared spectrometer. The borane molecule was produced with a discharge in a B2H6 and He mixture. The spectral pattern was consistent with the D3h structure of borane. The observed spectrum between 2450-2730 cm-1 was analyzed to determine band origins, rotational constants, and centrifugal distortion constants. The nu(3) band origins of (BH3)-B-11 and (BH3)-B-10 were 2601.5743(15) and 2615.7935(21) cm-1, respectively, with one standard deviation in parentheses. The B-H bond length was determined for the first time experimentally to be r0 = 1.190 01(1) angstrom from the ground state rotational constant B0.