A. van Wijngaarden

Quantum beats in the electric-field quenching of metastable hydrogen

The strong field-induced quantum beats observed in beam-foil studies of Ly- alpha radiation are obtained in a conventional metastable-hydrogen quenching experiment. The phase relation between the Stark shifted 2s1/2-2p1/2 Lamb-shift oscillations and the much more rapid 2s1-2p3/2 fine-structure oscillations depends on the detailed way in which the quenching field is switched on. Apart from a phaseshift, the results agree with a non-perturbative theoretical calculation which assumes that the field is applied suddenly. Various frequency components of the time-dependent radiation intensity are identified with specific hyperfine transitions or groups of transitions. No adjustable parameters are used for the initial state amplitudes.

Anisotropies and Lamb Shifts in Hydrogenicions Ions: Twenty Years of Progress

If a hydrogen atom (or other hydrogenic ion) is prepared in the metastable 2s½ state and then subjected to an external electric field, the induced Ly-α radiation to the ground state displays a rich diversity of quantum beats, anisotropics, and angular asymmetries resulting from a variety of interference effects. Over the past 22 years, these have been exploited at the University of Windsor to obtain fundamental measurements of the Lamb shift, decay rates, and the relativistic magnetic dipole (M1) transition amplitude. Table 1 summarizes the key developments since the anisotropy method of measuring the Lamb shift was first proposed in 1973.1 Peter Farago’s interest and enthusiasm played an important role during the early development stages.

Radiative Transitions in One- and Two-Electron Ions

This series of lectures has a rather general title because it deals with a variety of topics, both theoretical and experimental, which are related to one another. A great deal of progress has been made over the past few years in the precision of measurements for one- and two-electron atoms. A parallel development of new techniques for high precision caculations is opening the way to a wide variety of comparisons between theory and experiment which are sensitive to higher order relativistic and quantum electrodynamic (QED) effects. There are close connections between these lectures, which focus primarily on the low to intermediate range of nuclear charge, and those of Peter Mohr and Berndt Muller, which describe effects in the high nuclear charge and super-critical field regimes.