ELECTROMAGNETIC TRAPS FOR CHARGED AND NEUTRAL PARTICLES

Individual atomic and subatomic particles may be observed over long periods by confining them in “traps without material walls”. The Nobel Prize in physics was awarded in 1989 to Hans Dehmelt and Wolfgang Paul (together with Nor‐man F. Ramsey) for first introducing this concept. Such traps are made possible by extending the principles of two‐dimensional focusing of particles to three dimensions. This led, in turn, to precision radiofrequency spectroscopy and quadrupole mass spectrometry. For example, side‐band cooling, in which electrons absorb photons with an energy just below the resonance energy and use their kinetic energy to supply the balance, allowed an electron to be held for ten months in the center of a magnetic trap. In this way, ½ g was determined to be 1.001159652188(4). Copyright © 1990 by VCH Verlagsgesellschaft mbH, Germany