Calculation of the singlet-triplet energy differences using the universal function

A method to calculate the singlet-triplet energy differences in electron-atom (molecule) scattering is developed. The method uses the recently-developed universal function, which can extrapolate the generalized oscillator strength through the nonphysical region to K-2 (momentum transfer squared) = 0, to calculate the integral of the energy difference in the small K-2 region. Cubic spline is used for the experimental data to evaluate the contribution to the integral numerically. The energy differences in the transitions 1(1)S-2(1,3)P in e-He and X(1) Sigma(+)-A(1,3)Pi in e-CO scattering are calculated and compared with measurements as illustrative examples.