TRANSIENT LASER COOLING

We observed a new type of sub-Doppler cooling that employs neither pol arization gradients nor magnetic fields, and involves neither a dampin g force nor significant diffusive heating. Instead, light shifts combi ned with optical pumping (OP) to levels not coupled by the laser field gives transient cooling, and steady state is not achieved. The time s cale is set by the OP rate. We observe both cooling and heating, but o ften with the opposite detuning from that of steady state. A semiclass ical and a fully quantum mechanical calculation of transient cooling a gree very well with one another and with our data.