THEORETICAL-STUDY OF THE LOW-ENERGY BIN SPECTRUM

The ground XO(+)((1) Sigma(+)) and the three lowest a(1)l, a(2)0(-)((3 ) Sigma(+)) and b(1)0(+)((5) Sigma(+)) excited states of the BiN molec ule have been calculated employing the relativistic CI method based on effective core potentials. The calculated spectroscopic constants (T- e, r(e), and omega(e)) are in good agreement with experimental results , as also is the ground state D-e value computed to be 28400 cm(-1). T he a(2)O(-) state is predicted to lie 1740 cm(-1) higher than a(1)l. I t is shown that the b(1)O(+) state has a strongly perturbed potential curve with a shoulder on its repulsive limb due to an avoided crossing between the (5) Sigma(+) and (3) Pi states. This result explains the increase in its B-upsilon' constant with upsilon' found experimentally . The radiative lifetimes have also been calculated for all electric-d ipole-allowed transitions between the states considered.