LASER TRAPPING OF RADIOACTIVE FRANCIUM ATOMS

The difficult problem of quickly slowing and cooling nuclear reaction products so that they can be injected into a laser trap has been solve d by several groups and there are now strong efforts to work with the trapped atoms. The atoms are confined in the trap to a small spatial v olume of the order of 1 mm(3), but more importantly, they are also con fined in velocity, which makes them an ideal sample for spectroscopic measurements with other lasers. We have recently trapped radioactive f rancium and have embarked on a program to further study the francium a tom as a prelude to a test of the Standard Model analogous to previous work with Cs, Our sample of 3 min Fr-210 now contains over 20000 atom s, and is readily visible with an ordinary TV camera, We work on-line with the accelerator, and continuously load the trap to replace losses due to decay and collisions with background gas. We have maintained a sample of Fr atoms in the trap for over 10 hours, with occasional adj ustment of the trapping laser frequency to account for drifts, The pro posed test of the Standard Model will require accurate calculation of its atomic properties. We are currently testing these calculations by measuring other predicted quantities.