Author
R. W. Ditchburn
Bio: R. W. Ditchburn is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 14 citations.
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TL;DR: In this article, the authors present explicit models for a symmetry breakdown in the cases of the Weyl (or homothetic) group, the SL(4, R), or the GL(4-R) covering subgroup.
1,474 citations
TL;DR: In this paper, the development of the techniques of producing slow positron beams is traced from the original experiments and applications of such beams to the measurement of cross-sections for positrons interacting in various gases and for the production of positronium in vacuum is discussed in detail.
120 citations
TL;DR: In this article, the vibrational excitation processes which occur in molecular beam experiments on H2 molecules, and using H+ or H− as projectiles, are discussed from the theoretical viewpoint of the microscopic quantum dynamics and in relation to the various features of the two potential energy surfaces.
Abstract: The vibrational excitation processes which occur in molecular beam experiments on H2 molecules, and using H+ or H− as projectiles, are discussed from the theoretical viewpoint of the microscopic quantum dynamics and in relation to the various features of the two potential energy surfaces. The present study employs the vibrational close‐coupling–rotational infinite‐order sudden (VCC–RIOS) decoupling scheme and analyzes in detail the differences of behavior of the various inelastic differential cross sections in the small‐angle region. It is clearly found that two separate mechanisms can be invoked in the two systems to explain the differences in efficiency between the two excitation processes. Such mechanisms can be related in turn to specific features of the two potential energy surfaces and to their bearing on the final dynamical observables. Rather good agreement between calculated and observed cross sections is found for both systems.
39 citations
TL;DR: In this article, an effective potential model applicable to electron scattering by small or large molecules, including rotational and vibrational motions, was developed for electron scattering in N2, using the INDO/1s method to calculate the static potential at a large number of distances and a simple model was used for the polarization potential.
Abstract: An effective potential model applicable to electron scattering by small or large molecules, including rotational and vibrational motions, is developed for electron scattering by N2. The INDO/1s method is used to calculate the static potential at a large number of distances and a simple model is used for the polarization potential. The rotational and vibrational matrix elements of these potentials are accurately calculated and the scattering is treated by a truncated close‐coupling expansion. With no adjustable parameters, calculated electronically and vibrationally elastic scattering cross sections are in reasonable agreement with experiment for angles 40°–50° and less at energies 30–75 eV. The rotational excitation cross sections have never been measured for N2 but are predicted to be large (as large as half the pure elastic cross sections when integrated over scattering angles and larger than the pure elastic differential cross sections at a range of large scattering angles at each energy).
38 citations
TL;DR: In this article, it was shown that invariance of Lagrangian field theory under a class of the coordinate-dependent Lorentz group of transformations requires the introduction of a massless axial vector gauge field which gives rise to a super-weak long-range spin-spin force between particles in vacuum.
Abstract: It is shown that invariance of Lagrangian field theory under a class of the coordinate-dependent Lorentz group of transformations requires the introduction of a massless axial vector gauge field which gives rise to a super-weak long-range spin-spin force between particles in vacuum. Recent experiments demonstrating repulsion and attraction between circularly polarised laser beams are interpreted to be due to such a force enhanced by spin polarisation of sodium vapour, through which these beams pass.
23 citations