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A new method to deduce the neutron-electron scattering length from high-precision thermal-neutron measurements of the nuclear scattering length and of the scattering amplitudes of Bragg reflections is proposed. It consists of an extension of a Pendellösung interferometric technique proposed by Shull in 1968 to higher-order Bragg reflections in silicon. Error-bar estimates show that it could solve the ambiguity between disagreeing experimental values of the neutron-electron scattering length and provide a very precise temperature factor of silicon. © 2003 Elsevier Science B.V. All rights reserved., info:eu-repo/semantics/published, Proceedings of the WBW22 Workshop, dedicated to Prof. A.A. Lucas on his retirement (22nd Werner Brandt Workshop

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Siegert pseudostates are purely outgoing states at some fixed point expanded over a finite basis. With discretized variables, they provide an accurate description of scattering in the s wave for short-range potentials with few basis states. The R-matrix method combined with a Lagrange basis, i.e. functions that vanish at all points of a mesh but one, leads to simple meshlike equations which also allow an accurate description of scattering. These methods are shown to be exactly equivalent for any basis size, with or without discretization. The comparison of their assumptions shows how to accurately derive poles of the scattering matrix in the R-matrix formalism and suggests how to extend the Siegert-pseudostate method to higher partial waves. The different concepts are illustrated with the Bargmann potential and with the centrifugal potential. A simplification of the R-matrix treatment can usefully be extended to the Siegert-pseudostate method. © 2002 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

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A transformation of supersymmetric quantum mechanics for N coupled channels is presented, which allows the introduction of up to N degenerate bound states without altering the remaining spectrum of the Hamiltonian. Phase equivalence of the Hamiltonian can be restored by two successive supersymmetric transformations at the same energy. The method is successfully applied to the [Formula Presented] coupled channels of the nucleon-nucleon system and a set of Moscow-type potentials is thus generated. © 2000 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

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Supersymmetric transformations, i.e. factorizations of the radial Schrödinger equation, are generalized to potentials with a linear dependence on energy. These transformations are equivalent to generalized Darboux transformations and do not affect the energy dependence of the potential. A pair of transformations allows the removal of a bound state without modification of the phase shift. The method is applied to the removal of the forbidden bound states of a deep energy-dependent [Formula Presented] potential generating a phase-equivalent shallow potential with an [Formula Presented] repulsive core at the origin and the same energy dependence as the initial potential. © 2000 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

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The elastic [Formula Presented] and inelastic [Formula Presented] scatterings are studied with a coupled-reaction-channel three-body model for [Formula Presented] below 40 MeV. Without any parameter fit, the results agree fairly well with experiment for various deep and shallow [Formula Presented] potentials. In regions where no experimental data are available, the theoretical cross sections are sensitive to the choice of [Formula Presented] potential. The comparison of calculations with exactly phase-equivalent deep and shallow [Formula Presented] potentials deduced from supersymmetric transformations shows that this sensitivity is not related to the presence or absence of Pauli forbidden states. Assuming charge symmetry, we also calculate cross sections for the elastic [Formula Presented] and inelastic [Formula Presented] scatterings. The elastic cross sections of both mirror collisions display a strong backward rise for [Formula Presented] MeV. Below 10 MeV, the inelastic [Formula Presented] excitation functions are strongly enhanced by the long range of the [Formula Presented] first excited state. © 2000 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

En ce qui concerne la construction de potentiels équivalents, nous étendons les méthodes existantes à des catégories de potentiels très utilisées en physique nucléaire, à savoir les potentiels optiques (ou complexes), les potentiels en voies couplées et les potentiels dépendant linéairement de l'énergie. En utilisant une paire de transformations permettant d'enlever un état lié, nous comparons les propriétés physiques des potentiels nucléaires profonds (c'est à dire possédant des états liés interdits par le principe de Pauli) et peu profonds. Des calculs dans des modèles à trois corps du noyau à halo d'6He et de la collision 16O+17O à basse énergie n'ont pas révélé d'importantes différences entre ces familles de pot, Doctorat en sciences appliquées, info:eu-repo/semantics/nonPublished

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