Science
A Clearer View of Cold Atoms
Abstract
The sharpening of atomic energy levels with decreasing temperature is the motivation for using atoms cooled to just a fraction above absolute zero as the detection medium for metrological applications. Ultracold atom “fountains” already have been used in atomic clocks and in gravimeters and gravity gradiometers. However, the cooling process provides a thermal cloud of warmer atoms that surround the cold-atom core, and as detection of the atoms usually relies on monitoring fluorescence or absorption transitions between energy levels, these thermal atoms broaden the spectra and reduce sensitivity.