Charge-cloud distribution of Hg* (6³P₁) in e-e gamma experiments with polarized electrons

Abstract

Electron-impact excitation of the Hg*(63P1) state has been studied by means of electron-photon coincidences involving polarized electrons. Differential Stokes parameters (photon polarization components) have been determined for scattering angles ranging from 10 to 90' at E=8 eV and from 10 to 60' at E=15 eV. The state multipole formalism has been used to extract the charge-cloud distribution of the Hg*(63P1) state from the measured Stokes parameters at E=8 eV. At this energy shape and size of the charge-cloud distribution depend strongly on the direction of the electron polarization vector. The experimental data at E=8 eV are compared with R-matrix calculations where good agreement is obtained.

Total polarization of the 185 nm emission line of mercury excited by electron impact

“…Equation (5) applies again in this case and P 4 is the only Stokes parameter that can be different from zero due to symmetry arguments [10]. However, the natural isotope mixture leads to a much larger range for P 4 , namely 0.00 P 4 0.85, even for 'coherent excitation'.…”

“…Similar considerations as those outlined in subsection 2.2 lead to the conclusion that P 4 = 1 for excitation of the Hg (I = 0) isotope if spin effects (electron exchange and spin-orbit interaction for the continuum electron) are negligible. Equation ( 5) applies again in this case and P 4 is the only Stokes parameter that can be different from zero due to symmetry arguments [10]. However, the natural isotope mixture leads to a much larger range for P 4 , namely 0.00 P 4 0.85, even for 'coherent excitation'.…”

Electron Scattering by Atoms, Ions, and Molecules

“…Recent data for the ''integrated Stokes parameter'' in spin-polarized electron-impact excitation of Zn were reported by Pravica et al (2007). Figure 8.17 shows the apparatus of Sohn and Hanne (1992) used to determine generalized Stokes parameters for electron-impact excitation of mercury. More importantly, from the point of view of this review, it illustrates the essential features of many polarizedelectron studies.…”

“…Finally, the polarization of the incident beam is determined by measuring the left-right asymmetry of the accelerated outgoing electrons (without a target beam) scattered from a gold foil, making use of the spin-orbit effect in a so-called ''Mott detector.'' Similar apparatus were built by Berger and Kessler (1986) to measure the (generalized) STU-parameters for electron collisions with mercury and heavy noble gases, and by the Bielefeld group (Baum et al (2002) The polarized-electron apparatus of Sohn and Hanne (1992).…”

Electron excitation of the41P1state of a zinc atom

“…Due to the complexity and long time required for such experiments, the amount of available data on such collision systems is rather limited [1][2][3][4][5][6][7][8][9][10][11]. Therefore, more experimental results are still needed to test and develop the theoretical models.…”