Collision-induced coherent S + D excitation is investigated. A polarisation analysis of the subsequent D + P transition by the photon-particle coincidence method is not sufficient to completely determine the excitation amplitudes for the D state. Indeed, two distinct solutions are obtained. The electron distributions associated with these two are mirror images of one another in the plane determined by the normal to the scattering plane and the direction of maximum intensity of linearly polarised light, as measured from the direction of the normal. The Li(2s+ 3d) excitation induced by collisions with helium is studied both theoretically and experimentally in the keV energy range. The measurements confirm the existence of a theoretically predicted low-energy structure in the circular polarisation. The results are interpreted by generalising concepts previously developed for S + P excitation in quasi-one-electron systems.

Rotating compensator spectroscopic ellipsometry was used to study the optical properties of a rubbed polyimide layer. Two operating modes in the transmission configuration were studied. One was a conventional mode of `polarizer–sample–rotating compensator–analyzer'. The other was a dual rotation mode of `polarizer–rotating sample–rotating compensator–analyzer'. We found that calibration is not possible in the conventional mode due to the extremely small retardance and non-dichroic nature of the sample. Meanwhile, in dual rotation mode which we developed, a retardance smaller than 0.5° could be measured without calibration. Using this technique, the variation in retardance with rubbing could be easily determined over a range of 320–800 nm. The optical axis could also be determined with high precision for this sample, and this optical axis was found to be parallel to the direction of rubbing.

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