Crossed beam electron--electron scattering at 90degree and 300 eV

An extensive search of the literature has revealed no evidence that a primary isolation type experiment such as crossed beam electron--electron scattering has ever been performed at low energies. High energy scattering was first performed by a colliding beam technique at a total energy of 600 MeV in 1966. In the usual cathode ray tubes the density of residual gas molecules far exceeds the density of electrons. An analysis of crossed beam scattering equations revealed that if the electron beams intersected each other at an angle of 90degree the energy E' of electrons scattered in the direction of the c.m. velocity vector could range to as high as twice the primary beam energy E. Since electrons scattered from the residual gases would be expected to have energies < or =E, it seemed possible to separate the electron scattered electrons from the gas scattered electrons with an energy analyzer. We performed an extensive series of experiments using a parallel plate energy analyzer that revealed no significant results above the rather large background count. The experiments showed how difficult it is to detect the scattering with conventional apparatus. We next constructed an apparatus designed to detect almost all the electron scattered electrons that had energies greater than the retarding potential of a grid. The experiments were performed with beam energies of 300 eV and currents of 1.2 and 1.3 μA. The experimental results were compared to predictions based on Moller's quantum mechanical model for electron--electron scattering. A computer was programed to numerically integrate Moller's nonrelativistic c.m. differential cross section equation and the crossed beam equations due to Morse and Bernstein. We found the experimental results to agree well with theory