Dissociation energies of the molecules BCl and BCl+

The molecule BCl was generated by chlorination of B(s) with both MgCl2 and SrCl2 in a heated effusive beam source, and identified by mass spectrometry. Gaseous equilibria in the B-Mg-Cl and B-Sr-Cl systems were studied in the regions 1350-1600 K and 1760-1830 K, respectively, and the dissociation energy D-0 degrees(BCl)=121.3+/-1.1 kcal mol(-1) (5.26+/-0.05 eV) was derived from thermochemical analysis. When compared with a dissociation limit derived from a short upper state extrapolation, this result indicates a potential hump of about 6 kcal mol(-1) in the A (1) Pi state of BCl. Electron impact measurements yielded an ionization potential of 10.03+/-0.10 eV for BCl, which can be used to evaluate D-0 degrees(BCl+)=81.4+/-2.6 kcal mol(-1) (3.53+/-0.11 eV). Other values in the literature, some of which differ considerably from the new results, are discussed. (C) 1996 American Institute of Physics.