Absolute photoionization cross sections and resonance structure of doubly ionized silicon in the region of the 2p-1 threshold: experiment and theory
Mosnier, Jean-Paul and Sayyad, M. and Kennedy, Eugene T. and Bizau, J.-M. and Cubaynes, D. and Wuilleumier, F. and Champeaux, J.-P. and Blancard, C. and Varma, R. and Banerjee, T. and Deshmukh, P. and Manson, S. (2003) Absolute photoionization cross sections and resonance structure of doubly ionized silicon in the region of the 2p-1 threshold: experiment and theory. Physical Review A, 68 (5). 052712-1-052712-7. ISSN 1050-2947
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We present the absolute photoionization cross section of doubly ionized silicon as a function of photon energy. These were obtained by merging a Si2+ ion beam generated in an electron cyclotron resonance source with monochromatized synchrotron radiation from an undulator. The photoion yield measurements were carried out in the photon energy range between 95 eV and 170 eV, i.e., the region corresponding to the excitation followed by the ionization (threshold ∼133.8eV) of an inner-subshell 2p electron. Resonance structure due to 2p excitation in the 2p63s3p3P metastable state was also observed with its contribution to the total cross section not exceeding 3%. Calculation of the 2p photoionization continuum cross section as a function of photon energy was carried out using the relativistic random-phase approximation (RRPA) and agreed very well with the corresponding measurements. The resonance structure in the 3s cross section below the 2p threshold was found to be in good agreement with the multiconfiguration atomic structure calculations of Sayyad et al. [J. Phys. B 28, 1715 (1995)], while the corresponding RRPA-RMQDT (relativistic multi-channel quantum-defect theory) calculations proved less successful.
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