57 research outputs found
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
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
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
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
Enhancement of antihydrogen formation in antiproton collisions with excited-state positronium
© Published under licence by IOP Publishing Ltd. Antihydrogen formation in positronium scattering on antiprotons is investigated using the two-centre convergent close-coupling method. A several orders of magnitude enhancement in the formation of antihydrogen is found when positronium is in an excited state. The effect is greatest at the lowest energies considered which encompass those achievable in experiment. This suggests a practical approach to creating neutral antimatter for testing its interaction with gravity and for spectroscopic measurements
Asymptotic behavior of the Coulomb three-body scattered wave
Asymptotic forms of the scattered wave for a system of three arbitrary charged particles valid in all domains relevant to breakup are derived. The derivations are based on the relationship between the total wave function of a breakup process in a three-body system with Coulomb interactions and the wave function of the process of scattering of all three particles of the system in the continuum. The results are free from amplitude-phase ambiguity problems associated with previously known forms. A similar technique is used to obtain asymptotic forms of the three-body Coulomb Green’s function
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