Fourier transform infrared spectroscopy of BH3 with the first identification of the ν4 band

Abstract

High-resolution Fourier transform infrared spectra of the ν4 bands of 11BH3 and 10BH3 have been analyzed by taking into account Coriolis interaction between the ν4 = 1 and ν2 = 1 states in the 900–1300 cm−1 region. The main parameters thus obtained are the band origin ν4 = 1196.022(1), the rotational constant B4 = 7.9759(2), C4 = 3.84033(9), the first-order Coriolis coupling constant Cζ4 = -0.3255(2), the Coriolis interaction constant D24(~(2)1/2Bζ24) = 7.7065(3) cm−1 for 11BH3, and ν4 = 1201.805(7) B4 = 7.9662(7), C4 = 3.8466(3), Cζ4 = -0.3282(8), D24 = 7.631(1) cm−1 for 10BH3 with one standard deviation in parentheses. The ν2 band of 10BH was analyzed for the first time to determine ν2 = 1159.409(2), B2 = 7.8259(8), C2 = 3.8887(2) cm−1 and other constants. The observed absorption line intensities of the ν4 and ν2 bands were explained by using the ratio of the transition moments μ4/μ2 = 0.4. Assignments in the ν3 bands of 11BH3 and 10BH3 were extended with a set of newly determined ground state constants.