Classical atomic form factor

The general trends exhibited in the variation of the inelastic form factor in collisional transitions nl --> n'l', when l' is changed and n, l, and n' are kept fixed, are explained solely in terms of classical mechanics. Prev ious quantal results are reproduced from purely classical mechanics princip les. Our conclusions are valid not only for large quantum numbers (which pr ovide the usual classical correspondence) but also for other cases, which, up to now have been described only by quantal or semiclassical methods. The interesting trends exhibited in the form factor are directly reflected in experimental and theoretical treatments of collisions involving excited ato ms.