Rotational Spectrum of Borane IMonoammoniate: Boron and Nitrogen Hyperfine Structure and Vibrational Structure

The boron and the nitrogen hyperfine structure in the rotational spectra of two borane monoammoniate isotopomers, BH NH and BH ND have been investigated and the quadrupole coupling constants of boron and nitrogen have been determined. It was also possible to determine the spin rotation constants CN of boron. In the spectrum of BH NH we observed additional splittings which are not caused by quadrupole coupling. In the spectra of the ammonia dimer, (NH3)2, to our opinion the same kind of splittings occur. As interpretation of this phenomenon it was proposed that two different vibrational states cause the splitting. They were called ■x and ß. We use the same model for BH NH . The deuterated isotopomer BH ND shows the normal spectrum of a symmetric top with two coupling nuclei, similar to the deuterated ammonia dimer (ND3)2. We obtained the following results: BH ND in the x vibrational state, l/2(B + C) = 17517.21399(48) MHz, eQq B) - 2.584 (10) MHz, eQ g N) = -2.135 (5) MHz, C B) = 4.59 (87) kHz, BH NH in the ß vibrational state, 1/2(B + C) - 17517.27706 (52) MHz, eQq B) = 2.583 (8) MHz, eQq N) = -2.132 (5) MHz, C B) = 4.76 (99) kHz, and BH ND , 1/2 (B + C) = 15076.79992 (41) MHz, eQq B) = 2.550 (7) MHz, eQq N) = -2.169 (4)"MHz, C B) = 3.42 (67) kHz