Electron-impact excitation of the (5 d10 6s) S2 1/2 → (5 d10 6p) P2 1/2,3/2 resonance transitions in gold atoms

Results from a joint experimental and theoretical investigation of electron-impact excitation of the (5 d10 6s) S2 1/2 → (5 d10 6p) P2 1/2,3/2 resonance transitions in gold atoms are presented. The calculations were performed using three fully relativistic approaches, namely, a distorted-wave ansatz, a convergent close-coupling method, and a B -spline R -matrix method. The experimental data are independently normalized to the Bethe-Born formula using the currently preferred experimental values of the optical oscillator strengths. There is generally good agreement between the measured and predicted energy dependences of the integral cross section, provided that sufficient care is taken in the theoretical structure models to ensure that the proper optical oscillator strengths for the two transitions are obtained. A strong resonance feature seen only in the near-threshold excitation of the (5 d10 6p) P2 1/2 state is classified as a (5 d10 6 p2) D1 2 temporary state of the negative gold ion.