ATOMS IN CROSSED FIELDS - A NEW EXPERIMENTAL APPROACH

We describe a novel experiment on Rydberg atoms in crossed electric an d magnetic fields, recently performed at Imperial College. The novelty resides in a combination of a crossed-field geometry with a time-gate d detection technique, by which separation of the circularly polarized components is now achieved. The importance of achieving such a separa tion and the new opportunities it opens up an explained. By this appro ach, a map of the diamagnetic Stark patterns is obtained. The data exh ibit interesting behaviour in that the hydrogenic and non-hydrogenic g roups within the n-shell now become distinguishable. Their evolution a s a function of field strength brings out the difference between linea r and quadratic effects. The levels with a quadratic dependence on ele ctric held strength eventually invade and dominate the spectrum. We su rmise that the trend from order to chaos is different in crossed field s from the trend in the diamagnetic limit. We comment on further theor y required to clarify this point. Our observations extend up to and sl ightly above the saddle-point energy.