The electronic spectrum of Cr2

The electronic spectrum of Cr2 has been studied using multiconfigurational second-order perturbation theory. Potential curves for 18 electronic states have been computed. By employing an atomic natural orbital (ANO) basis set of the size 8s7p6d4f and by including 3s3p correlation effects and relativistic corrections, the following results were obtained (experimental data within parentheses): First, the location of two 1Σu+ states at 2.86 eV (2.70) and 2.51 eV (2.40) above the ground state. Second, spectroscopic constants for the a′ 3Σu+ state located 1.82 eV (1.76) above the ground state are: re = 1.67 Å (1.65 ± 0.02) and ΔG12 = 680 cm−1 (574). Third, a plausible candidate for the metastable state detected in 1985 by Moskovits et al. is the 5Σg+ state in the ground state manifold with the vibrational frequency ωe = 148 cm−1 (79 in a matrix). The vertical transition 5Σu+ ← 5Σg+ is 2.07 eV (2.11).