Auger-electron angular distributions calculated without the two-step approximation: Calculation of angle-resolved resonant Auger spectra of C_2H_2

Analytic expressions for the direct, resonant, and interference contributions to the differential cross section of a resonant Auger process, produced by the inner-shell photoionization of a linear molecule either “fixed in space” or belonging to a gas of randomly oriented molecules, have been derived following Dill’s procedures [ Dill et al. Phys. Rev. Lett. 45 1393 (1980)], but going beyond the two-step approximation. Angle-resolved Auger spectra of the C2H2 molecule measured on top of the C 1s→π* resonance [ Kivimäki et al. J. Phys. B 30 4279 (1997)] have been calculated together with asymmetry parameters, analyzing also the different contributions to the electron angular distributions