15min:

W. J. LAFFERTY, Optical Technology Division, NIST, Gaithersburg, MD 20899-8441; J.-M. FLAUD, Laboratoire de Photophysique Moléculaire, CNRS, Université de Paris Sud, Orsay, 91405 FRANCE; R. L. SAMS, T. A. BLAKE AND S. W. SHARPE, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352.

We are in the process of studying all the infrared active fundamentals of diborane; the spectrum from 280 cm^-1 to 2700 cm^-1 has been recorded, and band-by-band analysis is in progress. The analysis of the lowest frequency band centered near 369 cm^-1 , ₁₀, which results from the ring puckering vibration, will be presented in this talk. The spectrum of a sample with boron in natural abundance (19 % ¹⁰B, 81% ¹¹B) as well as one enriched in ¹⁰B has been obtained with a resolution of 0.0015 cm^-1 and a S/N of better than 500 to 1. This band appears to be the only unperturbed band in the diborane spectrum, and assignment of the three beautiful b-type bands of the ¹⁰B₂H₆, ¹⁰B¹¹BH₆ and ¹¹B₂H₆ isotopomers was straightforward despite the fact that the band centers of all three isotopomers fall within 0.05 cm^-1 of each other. In the enriched ¹⁰B sample the hot band, 2 ₁₀- ₁₀, could be completely assigned and spectroscopic constants obtained for the A_g 2 ₁₀ state.