CORE-POLARIZATION EFFECTS ON NEAR-THRESHOLD PHOTOIONIZATION OF MG

The multiconfiguration relativistic random-phase approximation theory (MCRRPA) is applied to the photoionization processes of Mg. Double-ele ctron excitations as well as core-electron excitations are included. T he core-electron excitations account for the core-valence correlations , specifically the core-polarization effects, and the double-electron excitations account for the intravalence correlations. We obtain a pre diction of the 3s(1/2) threshold photoionization cross section that is in excellent agreement with experiment. It shows that the core-polari zation effects in addition to the double-electron excitations play an important role in the near-threshold photoionization processes of Mg a nd the MCRRPA provides an accurate account of these effects. [S1050-29 47(97)04811-7].