Electron impact excitation of the 2²S[subscript 1/2] state of atomic hydrogen near threshold

Vita.Electron-hydrogen atom scattering is one of the most fundamental electron-atom scattering problems, providing excellent grounds for testing various theoretical approximation methods. Since the target atom wave functions and the forces of interaction are known exactly, any error in calculated scattering cross sections must be due solely to the approximation used to solve the three body Schroedinger equation. Thus experimental cross sections provide a basis for judging the accuracy of the theoretical techniques rather than the results of a particular calculation. An experiment to measure relative differential scattering cross sections from 0° to 180° for electron impact excitation of the metastable 2²S[subscript 1/2] state of atomic hydrogen is described. The metastable atom time of flight technique which is used is presented in detail along with a description of the apparatus constructed to perform the measurements. Preliminary experimental results are given