Kheifets, AnatoliBray, IgorHoszowska, J.2015-12-101050-2947http://hdl.handle.net/1885/51666We perform convergent close-coupling calculations of double photoionization (DPI) of the K -shell of alkaline-earth metal atoms (Be, Mg, and Ca) from the threshold to the nonrelativistic limit of infinite photon energy. Theoretical double-to-single photoionization cross-section ratios for Mg and Ca are compared with experimental values derived from high-resolution x-ray spectra following the radiative decay of the K -shell double vacancy. We investigate the role of many-electron correlations in the ground and doubly-ionized final states played in the DPI process. Universal scaling of DPI cross section with an effective nuclear charge is examined in neutral atoms in comparison with corresponding heliumlike ions.Keywords: Alkaline-earth metals; Convergent close-coupling calculations; Cross sections; Double photoionizations; Experimental values; Final state; Helium-like ions; High resolutions; K shells; Many-electron correlations; Neutral atoms; Nonrelativistic; Nuclear cha200910.1103/PhysRevA.79.0425042016-02-24