A Single Atomic Particle Forever Floating at Rest in Free Space: New Value for Electron Radius

Abstract

An updated survey of mostly experimental spectroscopy work in Seattle on an individual closely-confined isolated atomic or elementary particle is presented. The classical notion of an atomic particle at rest in free space is discussed, and shown to be approximable by zero-point confinement of the particle in a laboratory trap. An important tool for cooling the particle, and in the case of an electron, for obtaining directly the difference of spin and cyclotron frequencies vs, vc, is side band excitation. The quantum numbers of the geonium "atom", an electron in a Penning trap, have been continuously monitored in a non-destructive way by the new "continuous" Stern-Gerlach effect. In this way the g-factors of electron and positron have been determined to unprecedented precision,½g ≡ vs/vc ≡ 1.001 159 652 188(4),providing the most severe tests of QED and of the CPT symmetry theorem, for charged elementary particles. From the close agreement of experimental and theoretical g-values a new, 104 × smaller, value for the electron radius, Rg < 10-20 cm, may be extracted. Other important results are: confinement of the individual positron, Priscilla, for 3 months, a tenfold suppression of the natural width of the cyclotron resonance, detection of an isomeric (cyclotron-excited) state via mass-spectroscopy, isolation and continuous detection of an individual proton, confinement of ≈ 100 antiprotons slowed to ≈ 3000 eV, confinement of a Ba+ ion to 13 ≈ 100 nm, and the demonstration of quantum jumps in geonium and in an isolated, individual regular atomic particle, Ba+. Some new experiments are proposed.