Invariant graphical method for electron-atom scattering coupled-channel equations

We present application examples of a graphical method for the efficient construction of potential matrix elements in quantum physics or quantum chemistry. The simplicity and power of this method are illustrated through several examples. In particular, a complete set of potential matrix elements for electron-Lithium scattering are derived for the first time using this method, which removes the frozen core approximation adopted by previous studies. This method can be readily adapted to study other many-body quantum systems

Surface-integral formulation of scattering theory

We formulate scattering theory in the framework of a surface-integral approach utilizing analytically known asymptotic forms of the two-body and three-body scattering wavefunctions. This formulation is valid for both short-range and long-range Coulombic interactions. New general definitions for the potential scattering amplitude are presented. For the Coulombic potentials, the generalized amplitude gives the physical on-shell amplitude without recourse to a renormalization procedure. New post and prior forms for the Coulomb three-body breakup amplitude are derived. This resolves the problem of the inability of the conventional scattering theory to define the post form of the breakup amplitude for charged particles. The new definitions can be written as surface integrals convenient for practical calculations. The surface-integral representations are extended to amplitudes of direct and rearrangement scattering processes taking place in an arbitrary three-body system. General definitions for the wave operators are given that unify the currently used channel-dependent definitions

Interference between direct ionisation and positronium formation in continuum in positron-hydrogen collisions

The fully differential cross section for positron-impact ionisation of hydrogen is calculated in a two-centre Born approximation. It is suggested that two-centre approaches to the problem should assume incoherent combination of contributions from direct ionisation of the atom and positronium formation in continuum

Generalisation of scattering theory to charged particles

Generalisation of scattering theory to charged particles is presented. It is based on a surface-integral approach. New general denitions for the breakup amplitude in a three-body system valid for both short-range and long-range Coulombic interactions are given

Journal of Physics: conference Series

The convergent close-coupling calculations of e+-Li and e+-Na collisions are reported. The target is treated as one active electron interacting with an inert ion core. The positronium formation channels are taken into account explicitly utilizing both negative- and positive-energy Laguerre-based states. A large number of channels and high partial waves are used to ensure the convergence of the cross sections

Scattering theory with the Coulomb potential

Basic features of a new surface-integral formulation of scattering theory are outlined. This formulation is valid for both short-range and Coulombic long-range interactions. New general definitions for the potential scattering amplitude are given. For the Coulombic potentials the generalized amplitude gives the physical on-shell amplitude without recourse to a renormalization procedure. New post and prior forms for the amplitudes of breakup, direct and rearrangement scattering in a Coulomb three-body system are presented

Absolute differential cross sections for the electron impact excitation of the 12S → 22S + 22P levels of atomic hydrogen at 50 and 100 eV

Absolute experimental differential cross sections for the electron impact excitation of the 12S → 22S + 22P levels of H at 50 and 100 eV incident energy are obtained using an application of the method of mixtures and available accurate He (n = 2) experimental electron impact excitation differential cross sections. The determination of the number density composition of the mixed beam is made from energy loss measurements of the mixed beam at 200 eV and 25° scattering angle using accurate H and He theoretical differential cross sections obtained from the distorted-wave Born approximation [D. H. Madison (private communication)] and convergent close coupling [I. Bray and A. Stelbovics, Phys. Rev. A 46, 6995 (1992); D. V. Fursa and I. Bray, Phys. Rev. A 52, 1279 (1995)]

Electron-impact ionization of atomic hydrogen at 2 eV above threshold

The convergent close-coupling method is applied to the calculation of fully differential cross sections for ionization of atomic hydrogen by 15.6 eV electrons. We find that even at this low energy the method is able to yield predictive results with small uncertainty. As a consequence we suspect that the experimental normalization at this energy is approximately a factor of two too high.Comment: 10 page