Calculation ofS-matrix poles by means of analytic continuation in the coupling constant: Application to the2Πgstate ofN2−

Abstract

The method of analytic continuation in the coupling constant in combination with use of the statistical Pad\'e approximation is applied to the determination of resonance energy and width of the ${}^{2}{\ensuremath{\Pi}}_{g}$ state of ${{\mathrm{N}}_{2}}^{\ensuremath{-}}$. It is shown that standard quantum chemistry codes provide accurate data which can be used for analytic continuation in the coupling constant, and the resonance energy and width can be inferred with an accuracy comparable to other more elaborate methods.