Anticrossing Spectroscopy of Rydberg Atoms Using Blackbody Radiation

We report the observation of anticrossing signals arising from the interaction of 300-K blackbody radiation with Rydberg atoms near avoided crossings of Stark levels. The role of the blackbody radiation is roughly analogous to that of the resonance fluorescence in traditional anticrossing spectroscopy. We present preliminary results for avoided crossings of $\mathrm{ns}$ states with $n-2\mathrm{}$ Stark states in potassium for $n$ in the range 18-21.