Long-range dispersion coefficients for the low-lying electronic states of Mg2 from the calculation of the frequency-dependent dipole polarizabilities of Mg in its ground and excited states

The frequency-dependent dipole polarizabilities are calculated for the five lowest states 31S; 41S; 31P; 33P and 43S of Mg by using our time-dependent gauge invariant method (TDGI). Estimations of the long-range dispersion coefficients for all the first-molecular states dissociations of Mg2 are proposed. Accuracy of the results is checked through the calculations obtained from a length, a velocity and a mixed approach in the formulation of the oscillator strengths and the corresponding dynamic dipole polarizabilities. In all cases, the length results appear as a reference for the comparison with some previous works concerning the ground state. The long-range coefficients reported for almost all the low-lying states are new and predict a repulsive interaction between the 41S states.