Accurate ab initio rovibronic spectrum of the X 1Σg+ and B 1Σu+ states in Ar2

Using recently developed coupled-cluster response methods, accurate potential curves for the X 1Σg+ and B 1Σu+ electronic states of Ar2 are evaluated and the lowest rovibronic energy levels are calculated. The results are in very good agreement with the experimentally available spectroscopic data, and suggest a reassignment of the experimental vibrational numbering in the B 1Σu+ state.