Auger-electron angular distributions calculated without the two-step approximation: calculation of angle-resolved resonant Auger spectra of C2H2

Analytic expressions of 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 D et al 1980 Phys. Rev. Lett. 45, 1393], but going beyond the two-step approximation. Angle-resolved Auger spectra of the C2H2 molecule measured on top of the C 1s->pi* resonance [Kivimaki A et al. 1997 J. Phys. B: At. Mol. Opt. Phys. 30, 4279] have been calculated together with asymmetry parameters, analyzing also the different contributions to the electron angular distributions