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The authors describe a novel experimental technique, based on synchronizing pulsed Bitter coils with pulsed tunable laser sources in the ultraviolet, which allows a Faraday rotation method, originally developed for accurate f-value measurements of high Rydberg members with synchrotron radiation to be extended, both in available magnetic field strength and in spectral resolution. By applying their technique, they have extended accurate measurements of f-values for the principal series of Ba I from around n=15, where earlier measurements by the hook method become inaccurate, to n=42, well beyond the present capabilities of alternative experimental methods. Similarly, they have extended earlier magneto-optical measurements for Sr I from n=25 to n=43. Advantages of the new experimental approach are discussed.

We report new measurements off values for the principal series of Ba I for n values extending up to n = 42. The measurements, performed by Faraday rotation spectroscopy using a tunable dye laser, are believed to extend to higher values of n than any previous quantitative determinations. They cover a prominent series perturbation due io the 5d8p 'P, doubly excited autoionising line, and a comparison is made between our data and the predictions of multichannel quantum defect theory extrapolated from lower values of n.

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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