On Fri, 26 Jan 2007 14:00:07 -0800, Jim Kelley
quoting Brett:

Name me one instance where anyone has achieved taking a cesium atom to
absolute zero ...

Two Nobel prizes were won for doing this with Rubidium. Some may
recall that I already cited that as the other frequency standard
element (although rarely used as it is inferior to Cesium).

73's
Richard Clark, KB7QHC