High-Resolution Infrared Spectrum of the Ring-Puckering Band, ν10, of Diborane

Abstract

The spectrum of the ν10 band of diborane, arising from the ring-puckering 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 10B was recorded as well as one with naturally abundant boron, i.e., 64% 11B2H6, 32% 10B11BH6, and 4% 10B2H6. This mode is the lowest vibrational level of the molecule and is unperturbed, allowing a complete assignment of not only the fundamental bands but also the 2ν10–ν10 hot bands 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 shown that the harmonic approximation does not apply for ν10.