Theoretical treatment of predissociation of the CO (3sσ) B and (3pσ) C1Σ+ Rydberg states based on a rigorous adiabatic representation

Ab initio multireference configuration interaction calculations for adiabatic potential curves, nonadiabatic couplings 〈φi(R,r)|d/dR|φj(R,r)〉 and 〈φi(R,r)|d2/dR2|φj(R,r)〉, and nuclear kinetic energy corrections 〈dφi(R,r)/dR|dφi(R,r)/dR〉 for the (3sσ) B and (3pσ) C1Σ+ Rydberg states of the CO molecule have been carried out. The energy positions and predissociation linewidths for the observed vibrational levels of these two states have been determined in a rigorous adiabatic representation by the complex scaling method employing a basis of complex scaled harmonic vibrational functions in conjunction with the Gauss-Hermite quadrature method to evaluate the complex Hamiltonian matrix elements. The present treatment correctly reproduces the observed trends in energies and line broadening for vibrational levels of the B1Σ+ state and represents an improvement over the previous treatment in literature. The errors in the determined spacings of the v = 0–4 vibrational levels of the C1Σ+ state are less than 2% compared with measured data. The predissociation linewidths for the v=3,4 levels of the C1Σ+ state are found to be 4.9 and 8.9 cm−1, respectively, in good agreement with the observed values.