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The electron induced L3M two step double ionization cross sections of metallic Pd were determined experimentally for incident electron beam energies ranging from the double ionization threshold up to 18 keV. The double L3M ionization cross sections were derived from the intensity ratios [I(LaM):[I(La)] of the resolved M satellites to the parent diagram lines. The sample was bombarded with monoenergetic electrons from an energy tunable 20 kV electron gun. The diagram and M satellite x ray lines were measured by means of high resolution x ray spectroscopy using a reflection type von Hamos bent crystal spectrometer. The two step partial cross sections were determined by subtracting from the measured total double ionization cross sections the contributions due to the shake process and L1 L3M45 Coster Kronig transitions. Despite the thick target employed in the present study the dependence of the two step cross sections on the incoming electron energy could be derived using a target slice decomposition method. It is shown that the obtained energy dependence can be well reproduced by the semiempirical parametrization model of Pattard and Rost.

Single photon double K shell ionization of low Z neutral atoms in the range 12?Z?23 is investigated. The experimental method was based on measurements of the high resolution Kah hypersatellite x ray spectra following the radiative decay of the K shell double vacancy states excited by monochromatic synchrotron radiation. The photon energy dependence of the double K shell ionization was measured over a wide range of photon energies from threshold up to and beyond the maximum of the double to single photoionization cross section ratios. From the high resolution x ray emission spectra the energies and linewidths of the hypersatellite transitions as well as the Kah1:Kah2 intensity ratios were determined. The relative importance of the initial state and final state electron electron interactions to the K shell double photoionization is addressed. Physical mechanisms and scaling laws of the K shell double photoionization are examined. A semiempirical universal scaling of the double photoionization cross sections with the effective nuclear charge for neutral atoms in the range 2?Z?47 is established.