We have made high-accuracy measurements of the integrated Stokes parameters for resonance fluorescence from polarized electron-impact excitation of the 4p 5 5p͓5/2͔ 3 D 3 and 4p 5 5p͓5/2͔ 3 D 2 states of Kr. We report measurements in the region within 0.6 eV of threshold, which is below the first cascade threshold. We also present theoretical calculations of these Stokes parameters using a recently developed relativistic Breit-Pauli Rmatrix code. In well LS-coupled systems, nonzero values of the integrated Stokes parameter P 2 signal relativistic effects ͑like continuum spin-orbit coupling, i.e., Mott scattering͒. A single value of P 2 ϭ4(4)ϫ10 Ϫ3 at 12.0 eV was previously reported in this energy range ͓Furst et al., Phys. Rev. A 47, 3775 ͑1993͔͒. We have now measured P 2 at six different energies in this region to comparable precision. These results are consistent with P 2 ϭ0 and with the theory. We discuss the effect of the electron-beam energy width on the accuracy of the measurements. Even when such effects are accounted for, serious discrepancies remain between theoretical and experimental results for excitation of the intermediately coupled 3 D 2 state. ͓S1050-2947͑99͒07907-X͔ PACS number͑s͒: 34.80.Dp
We report operational and construction details of a simplified GaAs polarized electron source. It is contained in a modified 4.63 in. Conflat four-way cross, and uses a single 56 l /s turbomolecular pump. The design incorporates multiple cesiators to extend source lifetime, a new spring-clamp GaAs crystal mounting design to provide uniform crystal heating, and a very simple tubular 90°e lectrostatic deflector. We also discuss matters related to preparing, heat cleaning, and activating the GaAs crystal.
Using the computer program SIMION 6, we have studied the effects of spurious insulator charging on the trajectories of electrons through electrostatic tube lenses. We considered lens elements with flat ends, spaced a distance g apart, whose inner diameter Dϭ10g. For the standard cases of drift tubes, two-element lenses, and einzel lenses, we found that charging effects are eliminated if t/gϾ3.5, where t is the distance between the lens inner diameter and the charged spacing insulator.
A passive electrostatic recycling spectrometer for charged particles is described and demonstrated to store electrons with typical kinetic energies of tens of eV. The design of the charged particle optics and the basic operating characteristics of the storage ring are discussed. The storage lifetime achieved is approximately 50 micros, which is target gas pressure limited and corresponds to approximately 200 orbits of the 0.65 m orbital circumference. The storage ring also has controllable energy dispersive elements enabling it to operate as a spectroscopic device.
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