HIGH-RESOLUTION INFRARED STUDY OF THE NU(14), NU(17), AND NU(18) BANDS OF (B2H6)-B-11 AND (BBH6)-B-10-B-11

Using high-resolution Fourier transform spectra, a thorough analysis o f the nu(14) c-type, nu(17) a-type, and nu(18) a-type bands of both (B 2H6)-B-11 and (BBH6)-B-10-B-11 has been carried in the 10.3-, 6.2-, an d 8.5-mu m spectral regions, respectively. From this analysis a large set of precise ground state combination differences with J values up t o 36 (31) and K-a values extending to 18 (18) was derived for (B2H6)-B -11((BBH6)-B-10-B-11), These data were fitted using a Watson-type Hami ltonian leading to accurate ground state rotational constants. An r(s) value for the B-B distance has been determined to be 1.7645(10) Angst rom. The determination of upper state Hamiltonian constants proved to be much more difficult since the corresponding rotational levels of ea ch of the bands are strongly perturbed by nearby dark states. To accou nt for these strong localized resonances, it was necessary to introduc e the relevant interacting terms in the Hamiltonian matrix. As a resul t it was possible to calculate the upper state energy levels quite sat isfactorily. From these fits, estimates of the band centers and a few of the rotational constants of the resonating dark states were obtaine d. (C) 1998 Academic Press.