Physics Nobel: traps, clocks, quantum leaps.

Physics Nobel: Traps, clocks, quantum leaps

The Nobel Prize in Physics has often gone to researchers pondering the debris from atom-smashing experiments. The 1989 prize, however, honors a gentler approach to physics research, involving finely tuned masers and techniques for trapping a single electron or ion for long periods of time -- an ideal situation for making high-precision measurements and testing physical principles.

Half the prize goes to Norman F. Ramsey of Harvard University, who in 1949 improved an important technique for inducing atoms to shift from one energy level to another. Ramsey's approach of imposing two separate, oscillating electromagnetic fields on an atomic beam to induce energy-level transitions formed the basis for the cesium atomic clock, which sets the present time standard.

In the 1950s, Ramsey helped develop the hydrogen maser, in which excited hydrogen atoms fed into a cavity are carefully tuned to emit microwave radiation of a specific frequency. Because the hydrogen maser is more stable than the cesium clock over short periods of time, it is useful as a secondary time standard and for making high-precision frequency measurements.

Wolfgang Paul of the University of Bonn in West Germany shares the second half of the prize with Hans G. Dehmelt of the University of Washington in Seattle. Starting in the 1950s, Paul developed an electromagnetic trap cable of holding a small number of ions for long periods of time. The so-called Paul trap and its cousin, the Penning trap, play an important role in modern spectroscopy.

Dehmelt used ion-trap spectroscopy to study electrons and other charged particles. In 1973, he became the first to observe a single electron in a trap, opening the door to precise measurements of key electron properties (SN: 1/21/89, p. 38). Similar techniques allowed Dehmelt and his collaborators to observe a quantum jump in a single ion (SN: 6/21/86, p. 388).