Copyright (c) 2009 All rights reserved. http://works.bepress.com/bill_macgillivray Recent documents in Bill MacGillivray en-us Mon, 07 Sep 2009 17:03:52 PDT 3600 http://works.bepress.com/bill_macgillivray/10 http://works.bepress.com/bill_macgillivray/10 Mon, 07 Sep 2009 17:01:25 PDT Super-elastic scattering processes can be considered as the 'time reversal' of electron-photon coincidence measurements, with the advantage that data are accumulated thousands of times faster. This allows a far more extensive and accurate study of electron excitation of atoms which can also be excited using laser radiation. The application of a newly invented magnetic angle changing (MAC) device to these experiments has allowed the complete scattering geometry to be accessed for the first time, and experimental methods adopted in these new experiments are discussed here. Data are presented for excitation of the 41P1 state of calcium by electron impact at scattering angles from near 0 degrees to beyond 180 degrees, with incident energies of 45 eV and 55 eV. The results are compared to the DWBA theory of Stauffer and colleagues, with generally excellent agreement. Martyn Hussey http://works.bepress.com/bill_macgillivray/7 http://works.bepress.com/bill_macgillivray/7 Thu, 04 Sep 2008 20:55:12 PDT By utilising super-elastic electron scattering from laser excited atoms together with a new Magnetic Angle Changing device, it is possible to determine the differential cross sections for excitation of atoms by electron impact over the complete scattering geometry. In the experiments described here, these techniques are combined to reveal the angular momentum transferred to calcium atoms during electron excitation to the 41P1 state, from near zero degrees to beyond 180 degrees for the first time. The results significantly extend all previous data, and are compared to calculations based on a distorted wave Born approximation by Stauffer and colleagues. The experimental techniques are discussed, and results are presented for electron energies of 45eV and 55eV. Martyn Hussey http://works.bepress.com/bill_macgillivray/8 http://works.bepress.com/bill_macgillivray/8 Thu, 04 Sep 2008 20:54:42 PDT The interaction of near-resonant laser radiation with atoms immersed in a magnetic B field is calculated using a quantum electrodynamic model. In this model, the magnetic field is assumed to produce a small perturbation such that the degeneracy of the magnetic substates is lifted while maintaining the usual quantum numbers that define the states (the Zeeman effect). The laser radiation is considered to have a narrow bandwidth and to be temporally and spatially coherent. The model produces three general coupled differential equations that describe the state populations and their relative coherences and the optical coherences between levels coupled by the laser radiation. The model can therefore be directly applied to different experiments ranging from atom trapping and cooling experiments through to collision experiments carried out in magnetic and laser fields. Andrew James Murray