AN AB-INITIO INVESTIGATION OF THE INFRARED AND VISIBLE-UV SPECTRA OF BN+, AND PHOTOIONIZATION SPECTRUM OF BN

The low-lying quartet and doublet states of BN+ are reinvestigated the oretically by using multireference CI wavefunctions with a 6s5p3dlf ba sis set, The X(4) Sigma(-) ground state has a dissociation energy of 1 .13 eV. The first excited state is 1(2)II (T-e = 0.59 eV), with 1(2) S igma(-) lying O.11 eV higher. The infrared spectrum of X(4) Sigma(-) i s characterized by very low absorption intensities (1 congruent to 8 k m/mol for the fundamental absorption) and long emission lifetimes (4.9 s for v = 1 --> v = 0). Franck-Condon factors, oscillator strengths ( f(v'v '')) and radiative lifetimes (tau(v')) of the quartet-quartet tr ansitions A(4)II-X(4) Sigma(-), B-4 Sigma(-)-X(4) Sigma(-), B-4 Sigma( -)-A(4)II, and (CII)-I-4-X(4) Sigma(-) are given. The strongest absorp tion band corresponds to B-4 Sigma(-)-X(4) Sigma(-), with T-00 = 3.81 eV and f(00) = 0.0175. The longest lived quartet state is A(4)II, with tau(0) approximate to 21 mu s. The lifetimes of the B and C states (2 5 and 60 ns) are controlled by direct decay into the ground state rath er than by cascading processes. The best estimate for the adiabatic io nization potential X(3)II(BN) --> X(4) Sigma(-)(BN+) is 11.4 eV. A sep aration of 13.87 eV between X(4) Sigma(-)(BN+) and X(2) Sigma(+)(BN-), calculated at R(e)(BN+), agrees well with 13.8 +/- 0.3 eV determined by charge inversion spectrometry. Finally, a model photoionization spe ctrum of BN is proposed to assist in the experimental characterization of the ground state of BN (whether (II)-I-3 or (1) Sigma(+)) via the 1(2)II state of BN+.