High-resolution infrared spectrum of the ring-puckering band, nu(10), of diborane

The spectrum of the nu(10) band of diborane, arising from the ring-puckerin g vibration, has been obtained with a spectral resolution of 0.0015 cm(-1) in the region 275-400 cm(-1). The spectrum of a sample enriched in B-10 was recorded as well as one with naturally abundant boron, i.e., 64% (B2H6)-B- 11, 32% (BBH6)-B-10-B-11, and 4% (B2H6)-B-10. This mode is the lowest vibra tional level of the molecule and is unperturbed, allowing a complete assign ment of not only the fundamental bands but also the 2 nu(10)-nu(10) hot ban ds of all three boron isotopomers. The intensities of several hundred Lines of the fundamental and hot bands of all isotopomers have been measured and vibrational transition moments have been obtained. Finally, it has been sh own that the harmonic approximation does not apply for nu(10). (C) 2000 Aca demic Press.