THE NEGATIVE-ION BN- AND ITS ROLE IN DETERMINING THE GROUND-STATE OF BN VIA PHOTODETACHMENT - AN MRDCI AB-INITIO STUDY

Extensive multireference CI calculations using a contracted 6s5p3d1f G aussian basis set on the B and N atoms indicate that the X2SIGMA+, A2P I, and B2SIGMA+ states of BN- are bound with respect to the electron a ttachment BN + 3-. The 1(4)SIGMA+, 1(4)DELTA, and 1(4)SIGMA-, and 1(4) PI states of BN- are resonant states, all autodetaching into neutral B N. The electron affinity X3PI --> X2SIGMA+ is predicted to be 2.84 eV (with a best estimate of 3.10 eV). Other features studied for BN- incl ude the infrared spectrum of the X2SIGMA+ ground state as well as the electronic radiative properties involving the excited states A2PI and B2SIGMA+. The present study supports a X3PI ground state for BN, with a1SIGMA+ lying about 0.03 eV higher. As an alternative to optical spec troscopy on BN, experimental studies of the photodetachment spectrum o f BN- are proposed in order to find the ordering and energetic separat ion of the lowest 3PI and 1SIGMA+ states of BN.