We have determined the multiply differential cross sections (MDCS) of the vertical photo-double ionization of diatomic nitrogen with coincidence detection of the ejected electrons, for fixed and random orientations of the internuclear axis, using the correlated product of two two-centre continuum Coulomb functions for the description of the two ejected electrons, which satisfies the exact asymptotic conditions. To verify our procedure, we have applied it to the photo-double ionization of diatomic hydrogen for which many experimental and theoretical results are available. Our results on diatomic hydrogen show the influence of the initial state correlation. In the case of diatomic nitrogen only, the photo-double ionization of the 3σg orbital is considered resulting in the 1Σg state of the residual N dication. The case of the nearby 3Πu final state having an open shell configuration will be considered in a future paper. Our results confirm the symmetry properties of the MDCS and give the optimal ejection angles. A comparison is also made with results obtained by the Gaussian parametrization method.
Electron-impact double ionization of a helium atom in the presence of laser radiation with low frequency and intensity is studied theoretically. The kinematical regime of high impact energy and large momentum transfer, with one slow and two fast electrons in the final channel, is considered. Fully differential cross sections corresponding to the laser-assisted (e,3e) and (e,3 -\e) processes are calculated for different models of the target state. The angular distributions of the slow ejected electron are found to be seriously modified by the laser field and, in contrast to the field-free case, are strongly dependent on the electron-electron correlations in helium. At the same time, the laser-assisted (e,3 -le) results very slightly differ from those in the absence of a laser field.
Abstract. Understanding of particle dynamics is crucial in construction of electron guns, ion sources and other types of nonrelativistic beam devices. Apart from external guiding and focusing systems, a prominent role in evolution of such low-energy beams is played by particle-particle interaction. Numerical simulations taking into account these effects are typically accomplished by a well-known particle-in-cell method. In practice, for convenient work a simulation program should not only implement this method, but also support parallelization, provide integration with CAD systems and allow access to details of the simulation algorithm. To address the formulated requirements, development of a new open source code -Ef -has been started. It's current features and main functionality are presented. Comparison with several analytical models demonstrates good agreement between the numerical results and the theory. Further development plans are discussed.
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