THE INFRARED SPECTRUM OF THE $^{10}B_{2}H_{6}$ BANDS IN THE BRIDGE B-H STRETCHING REGION

Author Institution: Optical Technology Division, NIST; Laboratoire de Photophysique Mol\'{e}culaire, CNRS, Universit\'e Paris-Sud 91405; Anorganische Chemie FB9, Universit\""at-GHWe have been studying the spectrum of the $\nu_{13}$ region of $^{10}B_{2}H_{6}$ around $5 \mu m$ using high resolution Fourier transformed spectra of a pure isotopic sample. The $\nu_{13}$ band, arising from the bridge-hydrogen stretching vibration, is highly perturbed by numerous nearby lying combination levels. At this point we have performed an almost complete assignment of the $\nu_{13}$ fundamental as well as the much stronger combination band, $\nu_{v} + \nu_{15}$, and the $\nu_{g} + \nu_{15}$ band. The energy level fitting has proven to be very difficult. At the present stage six interacting states are included, including the three bright states $13^{1}, 5^{1} 1^{5}$ and $9^{1} 15^{1}$ and three dark states $7^{1} 14^{1}, 4^{1} 18^{1}$ and $3^{1} 5^{1}$. The observed energy levels are calculated in a satisfactory way but not to within the experimental accuracy (about $0.0002 cm^{-1}$). We hope to present a complete analysis including interaction constants between the resonating states