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

Abstract

Results for the three Stokes parameters (polarization components) P1, P2 and P3 of the VUV Hg transition 6s6p1P1 → 6s2 1S0 (185 nm) obtained from electron–photon (e, eγ) coincidence measurements at electron impact energies of 15 eV, 50 eV and 100 eV (Aussendorf et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2403) were combined to obtain the total degree of polarization . In addition, the Stokes parameter P4 was measured at an electron impact energy of 15 eV. The measured data are compared with predictions from a fullrelativistic distorted-wave calculation, a five-state semirelativistic Breit–Pauli R-matrix (close-coupling) model, and a convergent close-coupling ansatz, where relativistic effects are accounted for by recoupling of nonrelativistic results. In agreement with the theoretical predictions, no influence of the electron spin was observed for scattering angles θ ⩽ 30°. At 15 eV excitation energy and scattering angles θ ⩾ 40°, however, an increasing importance of spin effects is predicted.