DECELERATION AND COOLING OF A THERMAL BEAM OF RUBIDIUM.

Resonant radiation pressure from a pair of frequency-swept diode lasers has been used to decelerate and cool a thermal beam (200 degree C oven temperature, 5-mrad divergence) of rubidium to zero velocity. Both isotopes have been stopped. This method is nearly identical to that reported for the successful stopping of cesium. The two lasers were tuned to resonance with the two hyperfine components of the D2 line. This was necessary to counter the effects of optical pumping, which would otherwise have prevented the cooling process. The lasers were frequency swept at 2-3 times the 400-MHz Doppler width by an injected current ramp of a few tenths of a milliampere added to the normal 80-mA operating currents. During a flight time of 3-4 ms, each atom scattered approx 60,000 photons along a 1. 3-m path. The earth's field was not canceled, and there were no applied fields. The deceleration and cooling were observed by measuring the frequency dependence of the fluorescence induced by a short (200- mu s) pulse of light added to the end of each decelerating sweep. This probe pulse was generated by the same lasers that produced the cooling sweep.