Measurement of vacuum-assisted photoionization at 1 GeV for Au and Ag targets |
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Authors: | Dauvergne D Belkacem A Barrué F Bocquet J P Chevallier M Feinberg B Kirsch R Poizat J C Ray C Rebreyend D |
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Institution: | Institut de Physique Nucléaire, CNRS/IN2P3, Université Claude Bernard, Lyon I, 4 rue E. Fermi, F-69622 Villeurbanne cedex, France. |
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Abstract: | We report a measurement of photon impact ionization of K and L shell of Au and K shell of Ag targets in the 1-GeV energy range. We show that the cross section is dominated by a contribution from a new channel called vacuum-assisted photoionization. In this process the energy-momentum balance associated with the removal of the innershell electron is obtained by conversion of a high-energy photon into an electron-positron pair. This measurement is consistent with the theoretical prediction that vacuum-assisted photoionization is the most probable ionization mechanism at very high energies. |
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