Investigation of superelastic electron scattering by laser-excited Ba. Experimental procedures and results

Differential (in angle) electron scattering experiments on laser-excited ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$ ${}_{}{}^1{}_{}{}^{}P$ were carried out at 30- and 100-eV impact energies. The laser light was linearly polarized and located in the scattering plane. The superelastic scattering signal was measured as a function of polarization direction of the laser light with respect to the scattering plane. It was found at low electron scattering angles that the superelastic scattering signal was asymmetric to reflection of the polarization vector with respect to the scattering plane. This is in contradiction with theoretical predictions. An attempt was made to pinpoint the reason for this observation, and a detailed investigation of the influence of experimental conditions on the superelastic scattering was undertaken. No explanation for the asymmetry has as yet been found.