Interaction of blackbody radiation with xenon Rydberg atoms

Effects due to the interaction of 300 K background radiation with $\mathrm{Xe}\mathrm{}\left(\mathrm{nf}\right)\mathrm{}$ Rydberg atoms are reported. Transitions to nearby $d$ and $g$ levels are observed. When the ambient photon density is reduced to that appropriate to liquid-nitrogen temperature by cooling the apparatus, a corresponding reduction in the transition rates to these levels is observed. The transition rates are found to be consistent with those predicted by use of quantum-defect theory.