Measurements of the orientation and alignment parameters have been performed on potassium atoms using a superelastic scattering technique. In these experiments a laser beam is tuned to the 4 2 S 1/2 -4 2 P 3/2 transition in potassium. Electrons are scattered from these excited atoms and those electrons that gain energy in the collision are detected. These superelastic electrons carry information about the orientation and alignment parameters which describe the scattering process. Orientation and alignment parameters have been measured at an electron energy of 10 eV referred to the ground state and over an angular range from 0 • to 150 • . These parameters are in excellent agreement with those predicted using the convergent close-coupling theory.

The superelastic electron scattering technique has been employed to investigate the alignment and orientation parameters' dependence on electron energy for the 4 2S-4 2P resonance transition in potassium, with the aim of comparing experiment with theory as the electron energy is increased above different core ionization thresholds. Subsequent measurements of the angular dependence of the alignment and orientation parameters are presented over a wide range of scattering angles at superelastic electron energies of 4 and 80 eV. The differential cross section has also been extracted at an electron energy of 4 eV. The experimental data are compared with the convergent close-coupling calculation.

A complete set of spin-averaged parameters, including the differential cross sections and three Stokes parameters, were obtained from a series of superelastic scattering experiments on the 4 2P state in potassium. The four scattering parameters have been measured at an effective electron energy of 54.4 eV on the ground state and over an angular range from 0° to 145°. The experimental results are compared with a convergent close-coupling (CCC) calculation and several distorted-wave calculations together with previously reported measured differential cross sections. The excellent agreement between the CCC theory and the present measurements resolves a long-standing anomaly between theory and experiment at this energy in potassium.

A series of superelastic electron scattering experiments from lithium and from potassium is described in which the total polarisation parameter P+ is measured. We report significant departures from the coherence condition P+ = 1 for both targets. The structure observed in the parameter P+ can be interpreted by a qualitative wave mechanical model that had been introduced by our research group to explain similar structure in superelastic electron scattering experiments from sodium.