ROTATIONAL-EXCITATION OF DIATOMIC-MOLECULES AT INTERMEDIATE ENERGIES - ABSOLUTE DIFFERENTIAL STATE-TO-STATE TRANSITION CROSS-SECTIONS FOR ELECTRON-SCATTERING FROM N-2, CL-2, CO AND HCL

Absolute differential cross sections for the electron-impact rotationa l excitation of N-2, Cl-2, CO and HCl have been measured in a crossed- beam experiment. Results on rotational state-to-state transitions are obtained by a deconvolution procedure from the energy-loss peaks at pr imary energies between 10 eV and 200 eV and in the angular range from 10 degrees to 160 degrees. Details are given of an apparatus which all ows absolute measurements with high-energy resolution and excellent st atistics. At intermediate impact energies and scattering angles, unexp ected large angular-momentum transfer was found. The results are very different for various energies and for different molecules. Four excit ation mechanisms can clearly be distinguished. The experimental findin gs are compared with theoretical results using the semiclassical spect ator model and a close-coupling calculation with an effective interact ion potential.