10 research outputs found

    Investigation of spin-orbit effects in the excitation of noble gases by spin-polarized electrons

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    We have measured the integrated Stokes parameters of the light emitted following the impact excitation by polarized electrons of the np5 (n+1)p [5/2] 3 states in Ne (n=2), Ar (n=3), Kr (n=4), Xe (n=5), and the np5 (n+1) p[5/2] 2 state in Kr. The near-threshold linear-polarization fractions η1 were consistent with zero for all of the J=3 states measured, providing no evidence of Mott scattering. For J=2 excitation, η1 shows the clear influence of the intermediately coupled nature of the state. At threshold, the measured circular polarization η2 and linear polarization η3 for the J=3 states agree well with the LS-coupled threshold predictions. These results provide the basis for optical measurements of electron polarization

    Extrapolation procedures in Mott electron polarimetry

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    In standard Mott electron polarimetry using thin gold film targets, extrapolation procedures must be used to reduce the experimentally measured asymmetries A to the values they would have for scattering from single atoms. These extrapolations involve the dependence of A on either the gold film thickness t or the maximum detected electron energy loss in the target ΔE. Using a concentric cylindrical-electrode Mott polarimeter, we have studied and compared these two types of extrapolations over the electron energy range 20-100 keV. The potential systematic errors which can result from such procedures are analyzed in detail, particularly with regard to the use of various fitting functions in thickness extrapolations, and the failure of perfect energy-loss discrimination to yield accurate polarizations when thick foils are used. A critical discussion of previous work on this subject is presented

    Optical electron polarimetry with heavy noble gases

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    We have measured the polarization of fluorescence emitted by the noble gases He, Ne, Ar, Kr, and Xe following impact excitation by polarized electrons. In He, the 33P→23S transition was studied; in the heavy noble gases the np5 (n+1) p 3D3→np5 (n+1) s3P2 transitions were analyzed. We investigated these transitions as candidates for efficient optical electron polarimetry and found that, because of their larger excitation cross sections and analyzing power, the heavy noble gases are superior to He, which had been used previously as a polarimetric target. Several issues with regard to the implementation and accuracy of optical electron polarimetric techniques are discussed

    An attempt to observe Mott scattering optically

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    We report an attempt to make an optical observation of Matt scattering, involving the first studies of inelastic collisions between polarized electrons and a heavy noble gas. Polarization fractions of light emitted by the 5p56p[5/7],(3D3) state of Xe following impact excitation in an axial collision geometry were measured as a funclion of the incident electron energy, and compared with distorted-wave Bom calculations. The theoretical and experimental results agree qualitatively in the energy range where cascade contributions to the photon signal are small. We failed to measure non-zero values of the linear polarization fraction η1. which would have constituted unambiguous evidence for Matt scattering and/or the importance of higher-order excitation processes in this system

    Psychological distress and sleep quality among Sri Lankan medical students during an economic crisis.

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    ObjectivesThis study examined the evidence of the prevalence of psychological distress and poor sleep among medical students and its associations during an economic crisis.DesignThis was a cross-sectional study using an online questionnaire. It included the Depression Anxiety Stress Scales and Pittsburgh Sleep Quality Index (PSQI).Setting and participantsThis study included medical undergraduates from a large metropolitan university in Sri Lanka.Primary and secondary outcome measuresWe assessed the prevalence of psychological distress, sleep quality, and factors associated with psychological distress. To evaluate the associations, we used logistic regression.ResultsThe majority (69.2%) had some form of distress (depression, anxiety or stress), while 23% had distress in all three. Anxiety was the most prevalent (50.7%). Poor sleep quality was reported in 41%. The highest contribution to global PSQI was from sleep latency, duration, and daytime dysfunction subscales. In bivariate analysis, sleep quality was directly related to depression (t245.65 = -6.75, pConclusionsPoor sleep quality and psychological distress are high among the undergraduates. The findings emphasize the importance of addressing sleep quality and psychological wellbeing in medical undergraduates. Further research with larger and more diverse samples is needed for a more comprehensive understanding of the factors associated with psychological distress among undergraduates
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