We describe a novel experiment on Rydberg atoms in crossed electric and magnetic fields, recently performed at Imperial College. The novelty resides in a combination of a crossed-field geometry with a time-gated detection technique, by which separation of the circularly polarized components is now achieved. The importance of achieving such a separation and the new opportunities it opens up are explained. By this approach, a map of the diamagnetic Stark patterns is obtained. The data exhibit interesting behaviour in that the hydrogenic and non-hydrogenic groups within the n-shell now become distinguishable. Their evolution as a function of field strength brings out the difference between linear and quadratic effects. The levels with a quadratic dependence on electric field strength eventually invade and dominate the spectrum. We surmise that the trend from order to chaos is different in crossed fields from the trend in the diamagnetic limit. We comment on further theory required to clarify this point. Our observations extend up to and slightly above the saddle-point energy.
We report on experiments in which we have been able to actively cancel the motional Stark effect and observe pure diamagnetic spectra for the barium atom. These differ from those previously reported in that they contain no intruding structure. In addition, the sigma + and sigma - spectra have been found to be identical.
We report on one-photon laser spectroscopy experiments in which we have obtained the even z-parity diamagnetic spectrum of Sr by actively cancelling the motional Stark effect. This spectrum differs from previous experimental studies in that it contains no electric-field-induced structure. New calculations are reported at a resolution comparable with the experimental data, and an excellent agreement between theory and experiment is obtained.
We present a report on experiments performed at Imperial College on diamagnetic effects in many-electron atoms. These include both atomic-beam experiments with DC fields, for which the measurement technique involves detecting Rydberg atoms &er laser excitation. and experiments on columns of atomic vapour. in which case we have studied Faraday rotation induced by a pulsed magnetic field. In the atomic-beam experiments. interesting differences between the U + and U -spectra have been observed. We also describe theoretical work related to the interpretation of the data for both sets of experiments.
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