Rotational excitation by electron impact: a state selective study using laser-induced fluorescence

Angularly resolved pure rotational excitation of sodium dimers by intermediate energy electrons (150 to 300 eV) is studied using laser state selection technique, under nonresonant collision conditions. The experimental procedure, which is new to electron scattering, is described in detail. The experimental data show large rotational transitions and rotational rainbow structures. The relative cross sections agree well with the close coupling calculations and also with the spectator model predictions.