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One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr-Sommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. Manipulation of Rydberg states in free atoms and ions by single and multiphoton processes has been tremendously productive since the development of pulsed visible laser spectroscopy. The analogous manipulations have not been conducted for donor impurities in silicon. Here, we use the FELIX pulsed free electron laser to perform time-domain measurements of the Rydberg state dynamics in phosphorus- and arsenic-doped silicon and we have obtained lifetimes consistent with frequency domain linewidths for isotopically purified silicon. This implies that the dominant decoherence mechanism for excited Rydberg states is lifetime broadening, just as for atoms in ion traps. The experiments are important because they represent a step toward coherent control and manipulation of atomic-like quantum levels in the most common semiconductor and complement magnetic resonance experiments in the literature, which show extraordinarily long spin lattice relaxation times--key to many well known schemes for quantum computing qubits--for the same impurities. Our results, taken together with the magnetic resonance data and progress in precise placement of single impurities, suggest that doped silicon, the basis for modern microelectronics, is also a model ion trap. coherence | free electron laser | quantum information | picosecond population dynamics | hydrogenic donor impurity

Research was conducted to examine the potential problem with collisional radiative (CR) models where ground state atoms and ions travel through the plasma accompanied by excited atoms. Although excited atoms are few, their presence cannot be ignored due to the rapid manner with which they leave the plasma and return as ground state atoms. This leads to violations of particle conservation. Results demonstrate that the problem is in the use of the conventional CR model which cannot be remedied through a more sophisticated treatment of the recycling transport.

Antihydrogen has recently been produced in CERN. I discuss the original motivation for the study of antimatter, and describe the large, but as yet unsuccessful attempt to produce cold antihydrogen confined to a trap, where it can be studied spectroscopically, and compared with ordinary hydrogen. I also describe the experiment at CERN, which produced [approximately]11 atoms of antihydrogen moving at 90% of the speed of light, circumstances that make precision spectroscopy difficult.

This work describes the atomic route to laser isotope separation. This is a process which uses intense pulsed lasers to photoionize one isotopic species of a chemical element, after which these ions are extracted electromagnetically. The paper describes only the isotopic enrichment of uranium for nuclear fuel cycles. It makes brief mention of the traditional cascade processess used at present, and then turns to the atomic physics of laser photoionization. The principles of the laser isotope separation process, important spectroscopic experiments and considerations which determine the design of a plant are described. This review concentrates on the laser ionization process, few details of vaporization of uranium metal or the extraction of ions are given.

On Mar. 23, 1989, researchers Stanley Pons and Martin Fleischmann claimed that nuclear fusion was possible through the electrolysis of heavy water by a palladium cathode. This stunned the scientific community because it meant that a new source of energy was possible. Three weeks after the announcement, an investigative panel was formed with John R. Huizenga as co-chairman. He later wrote a book exposing the controversy of the new finding. The second edition of his book contains the latest developments in cold fusion after 1989 and a discussion of its political and scientific implications.

Small bubbles driven by an acoustic field in water glow. The properties of the light they emit seem to suggest that it has a black body spectrum, with no features specific to the atomic properties of the gas within the bubble, and that it is emitted in short pulses. In this review I describe experiments which have been done to measure properties of the light emission and the dynamics of the bubble wall. I concentrate on bubbles which contain noble gases, and fit the experimental spectra to a black body spectrum. The fits are shown to be generally good, and correspond to temperatures [approximately]25 000 K. I describe how a small bubble of noble gas can be expected to radiate at this temperature, and show that collisional excitation and pressure broadening can account for the observed spectrum, but that simple adiabatic compression of the gas tends to overestimate the source temperature, particularly for Ar and Xe. The significance of new experimental results on the pulse duration is stressed. I discuss theories of the collapse of the bubble, and describe calculations which show that non-uniform gas behaviour can be important. The sensitivity of the gas motion to the bubble collapse, and the ambiguities of the equations which describe the wall motion are discussed. I also give some details of an alternative theory based on quantum electrodynamics. Experiments on trapped helium are identified as the most simple, and a calculation based on the ideas described in this article is presented.

Recent research has produced evidence for non-exponential decay rates of unstable systems in relation to quantum mechanics. This is a prediction of quantum mechanics which has hitherto not been observed. The new experiment which has been developed as part of this research is capable of measuring pre-exponential decay. It also makes it possible to select both the duration of the pre-exponential region and the decay rate in the exponential region. It is not yet clear whether the same approach can be used to observe the quantum Zeno effect.