High-energy double photoeffect and photoionization with excitation from 2 S-1 and 2 S-3 states of helium-like ions

Double ionization and ionization with excitation of helium-like ions with Z much greater than 1 from 2(1)S and 2(3)S states on the absorption of a hig h-frequency photon have been considered. The analytical calculation is perf ormed in the non-relativistic photon energy range in the lowest order of pe rturbation theory in the inter-electron interaction. Coulomb wavefunctions and the Coulomb Green function are used as a zeroth-order approximation. Di fferential and total cross sections of the processes are expressed via the corresponding values for the single photoionization. The photoelectron ener gy spectrum is obtained in the marginal energy range (i.e. for p(1) much gr eater than p(2), p(1) and p(2) momenta of photoelectrons) for the double-io nization process. Simple relations between the cross sections of double ion ization and ionization with excitation are derived.