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 dev eloped and the relevant selection rules are given. Using recently obta ined R-matrix elements for the a (1) Delta(g) and b (1) Sigma(g)(+) ex citation of O-2, we have calculated orientation and alignment paramete rs for various scattering energies and angles. General features of the se parameters, which might be valid for excitation of other molecules as well, are pointed out. In particular it is shown that no rotation o f the electronic charge cloud around the molecular axis can be produce d during the collision.