Abstract
The atomic orientation J⊥+generated by polarized-electron impact excitation of Hg (6s2)1S0 →(6s6p)3P1 is studied using the electron–photon coincidence technique. J⊥+ shows asignificant dependence on the spin projection of the incident electrons. Experimentalresults are compared with theoretical predictions employing a semi-relativistic five-stateR-matrix(close-coupling) description and the relativistic distorted-wave approximation.The experimental data show, in qualitative agreement with the calculations, thatthe well established orientation propensity rules for light atoms are apparentlyviolated if the electron spin is initially down with respect to the scattering plane.The applicability of the propensity rules to electron-impact excitation of heavyatoms is analysed. The observed apparent violation is attributed to a quantummechanical interference caused by ‘intermediate coupling’ within the excited state.A re-evaluation of the data supports the validity of the orientation propensityrules.
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