Orientation in the 3P-3S transition in sodium induced by electron impact

Electron-collision induced orientation in Na has been measured for the 3 2 P to 3 2 S transition, the excited Na(3 2 P) being prepared by laser optical pumping. Incident electron energies have been 3, 10 and 20 eV at electron scattering angles theta col from 0 to 22.5 degrees . The experiment agrees well with close-coupling theory especially for 3 eV, while distorted-wave calculations need some improvement at low energies. The sign of the orientation is found to be positive indicating an attractive force. Interesting conclusions can be drawn for the phase parameter phi connecting scattering amplitudes to different magnetic substates.