SIGNIFICANT EVENTS - SCIENCE EVENTS
08/30/03

Cesium Atom in an Electric Field

When a neutral atom is placed in a uniform electric field, the electric charge around the atom rearranges itself to form a small electric dipole moment. This property is known as polarizability and varies by a factor of 120 between helium (the lowest) and cesium (the highest). The polarizability is responsible for many basic properties of atoms such as the van der Waals interaction and the dielectric constant. It can also lead to shifts in atomic clock frequencies such as those caused by the electric fields of black body radiation.

Harvey Gould and Jason Amini, at the Lawrence Berkeley National Laboratory, have, in a paper to be published in Physical Review Letters, reported a new measurement of the static dipole polarizability of the cesium atom. The measurement, which uses a fountain of laser-cooled cesium atoms, has an uncertainty of 0.14% - an increase in the measurement accuracy over previous tests by a factor of 14. It is of sufficient accurate to test calculations that include relativistic and core contributions to the polarizability. For details see http://arXiv.org/abs/physics/0305074.