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[en] The paper discusses some of the recent measurements of the fundamental physical constants and their ''constancy'' (particularly of those measurements relating to Lamb shifts, the fine structure constant, the Planck constant, the Rydberg constant, and the speed of light), and their implications for physics and spectroscopy. (orig.)
[en] A unitary transformation approach is used to study the energy level shift of the atom coupled to both a vacuum electromagnetic field and a driving laser. The Lamb shift of the energy levels is shown to depend on the Rabi frequency and the detuning of the driving laser, which couples another pair of levels.
[en] The 22S/sub 1/4/ interval (Lamb shift) in muonium was measured to be (1038 +/- 22) MHz in agreement with the prediction of QED. Muonium 2S atoms were formed by the beam-foil method at the Los Alamos Meson Physics Facility. The Lamb shift was measured by observing 2S-2P transitions induced by a microwave electric field. The microwave frequency was tuned from 800 MHz to 1400 MHz to drive the F = 1 → F = 0 and the F = 1 → F = 1 transitions. Measurements of the muonium formation probability are also reported and future experiments are discussed. An intense, pulsed source of thermal positronium was produced at the Lawrence Livermore Laboratory's 100 MeV electron linac. Pulses of 10 ns length containing 104 Ps atoms can be produced using an electron current of 3 μA at 120 pps. The time of flight method has been used to measure the Ps velocity distribution which was verified to be thermal
[en] Electromagnetic self-energy shifts for the 2S states of hydrogenic ions for Z = 10, 20, 30, 40, 50, 60, and 70 are presented. The results are computed nonrelativistically and with retardation according to a recent prescription of ours
[en] While taking into account the nuclear-structure contributions to the Lamb shift, one has to make various subtractions for the two-photon exchange contributions. Such subtractions should be consistent with the structureless part of theory. We study here the subtractions for a two-body atomic systems which consist of a pointlike lepton (an electron or a muon) and a nucleus with spin 0, 1/2, and 1, and find the recoil contribution in order (Zα)5 due to the subtractions for I = 0, 1. The related contribution to the energy levels for I = 1/2 of order (Zα)5*m is called the Salpeter term. (authors)
[en] Adapting an approach used by Feynman for the Lamb shift of an isolated atom, we obtain a nonperturbative expression for the Lamb shift of an atom in a dielectric medium, previously calculated perturbatively [P. W. Milonni, J. Mod. Opt. 42, 1191 (1995)]. The separation of the Lamb and Casimir components of the field energy is greatly simplified, and previous nonperturbative results for the Lamb shift [M. Schaden, L. Spruch, and F. Zhou, Phys. Rev. A 57, 1108 (1998)], based on the generalized argument theorem, are obtained much more easily and directly. copyright 1999 The American Physical Society
[en] In muonic atoms the Uehling potential (an effect of a free electronic vacuum polarization loop) is responsible for the leading contribution to the Lamb shift causing the splitting of states with Δn = 0 and Δl ≠ 0. Here we consider the Lamb shift in the leading non-relativistic approximation, i.e., within an approach based on a certain Schroedinger equation. That is valid for low and medium Z as long as (Zα)2 << 1. The results is a function of a few parameters, including κ Zαmμ/me, n and l. We present various asymptotics and in particular we study a region of validity of asymptotics with large and small κ. Special attention is paid to circular states, which are considered in a limit of n >> 1. (authors)
[en] The cooperative Lamb shift (CLS) is hard to measure because in samples much larger than a resonant wavelength it is much smaller, for an initially prepared resonantly phased state, than the cooperative decay rate (CDR). We show, however, that if the phasing of the initial state is detuned so that the spatial wave vector is k1 congruent with k0±O((1/R)) (where k0=ω0/c is the resonant frequency), the CLS grows to 'giant' magnitudes making it comparable to the CDR. Moreover, for certain controlled values of detuning, the initial CDR becomes small so that the dynamical Lamb shift (DLS) can be measured over a considerable period of time.