Configuration-interaction studies on the ground state and excited states of B2

Abstract
Using a 5s3p contracted Gaussian basis set, with additional d-polarization, s, p, d diffuse and p negative-ion functions, configuration-interaction (CI) methods were applied to the ground state and 55 low-lying states of B2. From the potential curves spectroscopic constants for 53 stable states were obtained. Experimentally, only the 23 Sigma -u-X 3 Sigma -g system is known. Agreement of calculated with experimental values for the two known states is very good. All-electron CI studies were performed for the two low-lying states X 3 Sigma -g and 15 Sigma -u, which are separated by only about 0.14 eV.