[en] In this work we present a correlated wave function for a three-body continuum Coulomb problem. This state is described by the two-variables PHI₂ hypergeometric function. We examine the properties of this function and their differences with previous uncorrelated models. The PHI₂ wave function can be considered as a final state of ion-atom ionizing collisions, giving rise to both undistorted (Born-PHI₂) and distorted (EIS-PHI₂) models. We obtain double differential cross sections with the Born-PHI₂ theory for proton-helium collisions in the intermediate to high energy regime. They exhibit all the main features of the electronic emission process and agree with the experimental data

[en] In this work we present a fully correlated wave function to describe the continuum of the three-body spectra for particles with arbitrary masses interacting with Coulomb potentials. We show that this function can be related with the PHI₂ correlated model introduced few years ago for ion-atom collisions processes. The function includes important properties such as correct asymptotic conditions and Kato's cusp conditions. We discuss the properties of the wave function for one heavy and two light particles, focusing in the case of positron-electron-proton systems. A comparison between the properties of the new model and the C3 one is also performed. This analysis suggests that this function can be a successful alternative choice for the description of positron-atom collisions

[en] First Born approximation (FBA) and continuum-distorted-wave endash eikonal-initial-state (CDW-EIS) approximation are used to calculate the cross section that is triply differential (TDCS) in the energy and angle of the emitted electron and scattered projectile for proton impact ionization of atomic hydrogen. The TDCS shows different prominent features, whose origin is examined on the basis of the results given by FBA calculations and reported for different physical effects. We discuss how these features are related to those present in the doubly differential cross section (DDCS). copyright 1996 The American Physical Society

[en] We present variational wave functions for He-like atoms with nuclear charge Z=1,...,10. We propose modifications of some usual simple correlated wave functions to account for the integration factor required in the evaluation of atomic ionization and excitation amplitudes with distorted wave methods. We determine the parameters of the trial functions and the resulting energies. We introduce new procedures to test the cusp conditions at the singularities of the Coulomb field

[en] Our aim is to study the ionization-excitation and (e,3e) processes of the He atom. The high energy first Born-approximation transition amplitudes are obtained from the asymptotic limit of the exact three-body wave function. This wave function is obtained by solving a driven Schrödinger equation which contains the double bound He wave function. The resulting equation is solved using Generalized Sturmian functions.

[en] In this work we present the application of the generalized Sturmian basis to the single photon - double ionization of atoms.

[en] We introduce a method of obtaining volume integrals involving confluent hypergeometric functions. This method is based on the integral representation of these functions and enabled us to write a generalized Nordsieck integral in terms of hypergeometric functions of many variables. We explore some particular results that could be useful when calculating transition matrices in collision theories. copyright 1997 American Institute of Physics

[en] In this letter, a set of ground state wavefunctions for the He atom is given. The functions are constructed in terms of exponential and power series as similar as possible to the Hylleraas functions of Chandrasekhar and Herzberg (1955 Phys. Rev. 98 1050). The accuracy of the calculated energies is found to be about 10^-4 au and all the cusp conditions at the Coulomb singularities are satisfied. The nine-parameter functions proposed here are found to have better local energy than those given by the 6 and 14 terms Hylleraas functions of Chandrasekhar. The mean value of various functions evaluated with the different proposals shows their good quality. These properties highly qualify the function to be used as an alternative to the Chandrasekhar functions in collisional problems. The whole set of functions given here can be considered as an alternative to the proposals of Chandrasekhar (1955 Phys. Rev. 98 1050), Bonham and Kohl (1966 J. Chem. Phys. 45 2471) and Le Sech (1997 J. Phys. B: At. Mol. Opt. Phys. 30 L47). (letter to the editor)

[en] We studied the doubly differential cross section (DDCS) for ion-helium ionization, in the region of near zero emission velocity. We expanded the DDCS in powers of the electron emission velocity, with angle-dependent weight coefficients, which are determined from available experimental data and calculated using the CDW-EIS theory. We also compared this expansion with a previously used Legendre polynomials expansion of the DDCS. (orig.)

[en] We study the effect of electron-ion correlation in single ionization processes of atoms by ion impact. We present a distorted wave model where the final state is represented by a correlated function solution of a non-separable three-body continuum Hamiltonian, that includes electron-ion correlation as coupling terms of the wave equation. A comparison of the electronic differential cross sections computed with this model with other theories and experimental data reveals that the influence of the electron-ion correlation is more significant for low energy emitted electrons. (author). Letter-to-the-editor