ABINITIO CALCULATION OF NUCLEAR-QUADRUPOLE COUPLING-CONSTANTS OF ROVIBRATIONAL LEVELS OF (BH)-B-11-H-2, (BH)-B-10-H-2, AND (BH)-B-10-H-1 INTHE DOUBLE-MINIMUM B (1)SIGMA(+) ELECTRONIC STATE

The B-11, B-10, and H-2 quadrupole coupling constants of rovibrational levels of (BH)-B-11-H-2, (BH)-B-10-H-2 and (BH)-B-10-H-1 in their B1S IGMA+ state were calculated from molecular wavefunctions which explici tly describe nuclear displacement. The electric field gradient as a fu nction of the internuclear distance was computed by use of the multi-r eference configuration interaction approach, the radial rovibrational wavefunctions were obtained by the Fourier grid Hamiltonian method. Th e double-minimum character of the potential is seen to markedly influe nce the rovibrational dependences of the boron and deuteron coupling c onstants. The quadrupole hyperfine structure of all vibrational levels of (BH)-B-11-H-2 and (BH)-B-10-H-2 isotopomer is essentially determin ed by the relatively strong boron coupling which is perturbed by the d euteron coupling.