Energy dependence of the gaussian description of the TDCS for equal energy sharing photo-double-ionization

S. OTRANTO, F. D. COLAVECCHIA, C. R. GARIBOTTI

Rosario, Argentina

Conferencia; XXI International Conference on Photonic Electronic and Atomic collisions (ICPEAC); 2005

For PDI of He, the triply differential cross section (TDCS) in the equal energy sharing regime can be factorized as a term that describes the electron-photon interaction times a function in the interelectronic angle q12, the excess energies Ef and nuclear charge Z [1]:q12, the excess energies Ef and nuclear charge Z [1]:Z [1]:       ds              = C(q12, Ef, Z)(cosq1+ cosq2)2 dW1 dW2dEf   During the last few years, the Gaussian shape for the correlation factor has become of standard use for experiments interpretation, with its full width at half maximum considered as an empirical parameter [2]. In recent papers we introduced a new theoretical method to describe the continuum state of two electrons in the field of an ion [3]. This method modifies the electron-electron interaction in the C3 wave through the introduction of a multiplicative parameter b that acts on the relative distance between these particles, and indirectly accounts for the dynamical screening effect of the nuclear ion. This parameter is selected to avoid the exponential decay of the total PDI cross section at low photon energies derived from the C3 model. We have denoted this wave function as SC3. Triply differential cross sections (TDCS) evaluated with the SC3 wave function improve C3 results. In this work, we analyze possible generalizations for the single Gaussian correlation factor for the intermediate to high energy limit, where different emission mechanisms compete. In the figure we show G(Ef , Z) as a function of distance between these particles, and indirectly accounts for the dynamical screening effect of the nuclear ion. This parameter is selected to avoid the exponential decay of the total PDI cross section at low photon energies derived from the C3 model. We have denoted this wave function as SC3. Triply differential cross sections (TDCS) evaluated with the SC3 wave function improve C3 results. In this work, we analyze possible generalizations for the single Gaussian correlation factor for the intermediate to high energy limit, where different emission mechanisms compete. In the figure we show G(Ef , Z) as a function ofb that acts on the relative distance between these particles, and indirectly accounts for the dynamical screening effect of the nuclear ion. This parameter is selected to avoid the exponential decay of the total PDI cross section at low photon energies derived from the C3 model. We have denoted this wave function as SC3. Triply differential cross sections (TDCS) evaluated with the SC3 wave function improve C3 results. In this work, we analyze possible generalizations for the single Gaussian correlation factor for the intermediate to high energy limit, where different emission mechanisms compete. In the figure we show G(Ef , Z) as a function ofG(Ef , Z) as a function of E1/4 for He target for PDI of He. We have also included the experimental values obtained by different authors, and the results given by the CCC method [4]. For very low energies the linear dependence with E1/4 derived from the Wannier mechanism is satisfied, but as energy increases a tendency to saturation could be devised in theoretical and experimental values. This could be interpreted as a stabilization of the angular correlation produced by the atomic ion.1/4 for He target for PDI of He. We have also included the experimental values obtained by different authors, and the results given by the CCC method [4]. For very low energies the linear dependence with E1/4 derived from the Wannier mechanism is satisfied, but as energy increases a tendency to saturation could be devised in theoretical and experimental values. This could be interpreted as a stabilization of the angular correlation produced by the atomic ion.E1/4 derived from the Wannier mechanism is satisfied, but as energy increases a tendency to saturation could be devised in theoretical and experimental values. This could be interpreted as a stabilization of the angular correlation produced by the atomic ion. Figure 1: G as a function of E1/4 for He target. Theories: solid-line: SC3 model, dashed-line: CCC ref. [4]. References [1] A. Huetz and J. Mazeau, Phys. Rev. Lett. 85, 530 (2000). [2] G. King and L. Avaldi, J. Phys. B: At. Mol. Opt. Phys. 33, R215 (2000). [3] S. Otranto and C.R. Garibotti, Eur. Phys. J. D 21, 285 (2002); Eur. Phys. J. D 27, 215 (2003); Nucl. Instr. and Meth. B 222, 19 (2004). [4] A.S. Kheifets, I. Bray, Phys. Rev. A 62, 065402 (2000). Figure 1: G as a function of E1/4 for He target. Theories: solid-line: SC3 model, dashed-line: CCC ref. [4]. References [1] A. Huetz and J. Mazeau, Phys. Rev. Lett. 85, 530 (2000). [2] G. King and L. Avaldi, J. Phys. B: At. Mol. Opt. Phys. 33, R215 (2000). [3] S. Otranto and C.R. Garibotti, Eur. Phys. J. D 21, 285 (2002); Eur. Phys. J. D 27, 215 (2003); Nucl. Instr. and Meth. B 222, 19 (2004). [4] A.S. Kheifets, I. Bray, Phys. Rev. A 62, 065402 (2000).