ROTATIONALLY RESOLVED EXCITATION OF DIATOMIC-MOLECULES BY ELECTRON-IMPACT

We consider the rotationally resolved excitation of homonuclear Hunds case (b) molecules by unpolarized electrons. The general theory is developed and the relevant selection rules are given. Using recently obtained R-matrix elements for the a (1) Delta(g) and b (1) Sigma(g)(+) excitation of O-2, we have calculated orientation and alignment parameters for various scattering energies and angles. General features of these parameters, which might be valid for excitation of other molecules as well, are pointed out. In particular it is shown that no rotation of the electronic charge cloud around the molecular axis can be produced during the collision.