Abstract

Francium, the heaviest alkali, has no stable isotopes and has eluded extensive study because sufficient quantities have not been available for detailed investigations. The strong phase space confinement makes the magneto-optic trap a very good tool for spectroscopic studies that can lead to measurements of atomic parity violations in francium. We have succeeded in injecting into a magneto-optical trap ^2l0Fr atoms (half-life 3.2 min.) produced in the reaction ¹⁹⁷Au(¹⁸O, 5n) → ²¹⁰Fr at the Stony Brook Superconducting LINAC. The nuclear reaction takes place in a low vacuum region. The products are extracted as ions and transported to a high vacuum region where they are neutralized on an yttrium surface. They enter a glass cell, where six laser beams with the appropraite polarization intersect in the presence of a 10 G/cm magnetic field gradient. The glass cell is coated with an organosilicon to prevent sticking of the francium and permit multiple bounces through the trapping region. The trapped atoms are observed by modulating the trapping laser frequency and detecting the modulation of the trap fluorescence with a lock-in amplifier. The number of atoms trapped is estimated to be more than 500. The narrowness of the trap signal and the high signal to noise ratio allowed measurement of the location of the cycling transition of the trap with respect to a close tabulated molecular iodine line.

© 1996 Optical Society of America