History:
Marguerite Perey of the Curie Institute in Paris reported in 1939 the discovery of a new radioactive element. She found it while analyzing the radioactive decay products of actinium. She named the new element francium after her country.
The study of its physical properties has been limited by availability. During the 1970s and 1980s a team led by Sylvain Lieberman studied its atomic structure. They produced francium at CERN using the isotope separator ISOLDE. The result after ten years of experiments was a map of some of the energy levels and hyperfine structure of different isotopes.
The group of Letokhov from Moscow University used a radioactive source to study the properties of some highly excited states. They developed a very sensitive way of detecting the ionization of a single francium atom.
| The Stony Brook group started its pursuit of francium in 1991. The combination of the heavy ion superconducting linear accelerator at the NUCLEAR STRUCTURE LAB is capable of producing a few francium atoms and the expertise of laser trapping and cooling in the ATOMIC PHYSIC GROUP has made the enterprise possible. Stony Brook began a program to produce and then capture francium in a laser trap. Since the trapping of radioactive atoms was a novel field, the Stony Brook team first trapped radioactive 79 rubidium. In September of 1995 the team succeeded for the first time in capturing a few thousand atoms of the isotope 210 of francium. The atoms remained trapped for about 20 seconds by the interaction with six laser beams in the presence of an inhomogenous magnetic field. By January of 1996 the fluorescence from the trapped francium atoms was visible with a camera. |  Figure 1. False color image of francium atoms trapped with lasers. The central spot is about 1 mm in diameter. The other bright areas come from laser light scattered off of glass surfaces.
Animated image of trap forming as laser frequency is scanned. Prepared by Mary F. Ifferte, Stony Brook Physics Major |
