Dehmelt

H. G. Dehmelt (University of Washington, Seattle) and W. Paul (Bonn) development of the ion trap technique. 

The electric mass filter is the basis for the electrodynamic trap used for studies of the spectroscopy of atomic ions that earned Paul and Dehmelt the 1989 Nobel Prize in Physics. A wide variety of electrode configurations can be used to trap particles, and a particularly simple design was proposed by Straubel (1956). His dc electrodes were flat plates, and the ac electrode was a simple torus or washer placed at the midplane between the endplates. 

This review of the chemistry and physics of microparticles and their characterization is by no means comprehensive, for the very large range of masses that can be studied with the electrodynamic balance makes it possible to explore the spectroscopy of atomic ions. This field is a large one, and Nobel laureates Hans Dehmelt and Wolfgang Paul have labored long in that fruitful scientific garden. The application of particle levitation to atmospheric aerosols, to studies of Knudsen aerosol phenomena, and to heat and mass transfer in the free-molecule regime would require as much space as this survey. 

Dehmelt, H. Experiments on the Structure of an Individual Elementary Particle, Science, 539 (February 2, 1990). 

Current theories of particle physics predict that, in a vacuum, the positron is a stable particle, and laboratory evidence in support of this comes from experiments in which a single positron has been trapped for periods of the order of three months (Van Dyck, Schwinberg and Dehmelt, 1987). If the CPT theorem is invoked then the intrinsic positron lifetime must be > 4 x 1023 yr, the experimental limit on the stability of the electron (Aharonov et al., 1995). 

To effectively form a bound antiproton-positron state starting from free particles, excess energy and momentum has to be carried away by a third particle. Various schemes for producing antihydrogen have been proposed and discussed in some detail [21,22,23,24,25,26,27], with the first mention of the possible production of antihydrogen in traps by Dehmelt and co-workers [28],... 

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