INPLANE POLARIZATION CORRELATION STUDY OF THE 3(1)D STATE OF HELIUM EXCITED BY 40 EV ELECTRONS

Electron-photon polarisation correlations measured in the scattering p lane defined by the incident and scattered electron momenta are report ed for 40 eV electron impact excitation of the 3 1D state of helium an d for electron scattering angles in the range 40-degrees less-than-or- equal-to theta less-than-or-equal-to 120-degrees. When combined with t he results of our earlier polarisation analysis on radiation emitted p erpendicular to the scattering plane, detailed information on the shap e and dynamics of the exicted state is obtained. In the small angular range of overlap (40-60-degrees) there is excellent agreement with a p ervious experimental study. The behaviour of the linear polarisation o f the radiation emitted in the scattering plane is well reproduced by a multichannel eikonal theory for theta less-than-or-equal-to 80-degre es. Otherwise theories totally fail to described the excitation proces s.