Trilobites and other molecular animals: How Rydberg-electrons catch ground state atoms

We report on laser spectroscopy results obtained in a dense and frozen Rydberg gas. Novel molecular bonds resulting in ultralong-range Rydberg dimers were predicted [1] and dimers as well as trimers in different vibrational states were found [2]. Some of these states are predicted to be bound by quantum reflection. Lifetime measurements confirm this prediction. Coherent superposition between free and bound states have been investigated [3]. Recently we have also confirmed that in an electric field these homonuclear molecules develop a permanent dipole moment [4]. \\[4pt] [1] C. H. Greene, A. S. Dickinson, and H. R. Sadeghpour, \textit{Phys. Rev. Lett.} \textbf{85}, 2458 (2000). \\[0pt] [2] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. L\"{o}w, T. Pfau, \textit{Nature }\textbf{458}, 1005 (2009), V. Bendkowsky, B. Butscher, J. Nipper, J. Balewski, J. P. Shaffer, R. L\"{o}w, T. Pfau, W. Li, J. Stanojevic, T. Pohl, and J. M. Rost, \textit{Phys. Rev. Lett. }\textbf{105}, 163201 (2010). \\[0pt] [3] B. Butscher, J. Nipper, J. B. Balewski, L. Kukota, V. Bendkowsky, R. L\"{o}w, and T. Pfau \textit{Nature Physics }\textbf{6}, 970--974 (2010). \\[0pt] [4] W. Li, T. Pohl, J. M. Rost, Seth T. Rittenhouse, H. R. Sadeghpour, J. Nipper, B. Butscher, J. B. Balewski, V. Bendkowsky, R. L\"{o}w, T. Pfau, \textit{Science }\textbf{334}, 1110 (2011).