We report on the realization of high resolution electron microscopy of Rydbergexcited ultracold atomic samples. The implementation of an ultraviolet laser system allows us to excite the atom, with a single-photon transition, to Rydberg states. By using the electron microscopy technique during the Rydberg excitation of the atoms, we observe a giant enhancement in the production of ions. This is due to l-changing collisions, which broaden the Rydberg level and therefore increase the excitation rate of Rydberg atoms. Our results pave the way for the high resolution spatial detection of Rydberg atoms in an atomic sample. − 500 V cm 1 ) or electric field gradients ( − 200 V cm 2 ) in the center of the chamber, which are of 2 New J. Phys. 16 (2014) 083034 T Manthey et al

We characterize the two-photon excitation of an ultracold gas of rubidium atoms to Rydberg states analyzing the induced atomic losses from an optical dipole trap. Extending the duration of the Rydberg excitation to several milliseconds, the ground-state atoms are continuously coupled to the formed positively charged plasma. In this regime we measure the n dependence of the plasma-induced blockade effect and we characterize the interaction of the excited states and the ground state with the plasma. We also investigate the influence of the quasielectrostatic trapping potential on the system, confirming the validity of the ponderomotive model for states with 20 n 120.

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Shock waves in argon and in air have been observed when focusing a 0.8 J, 40 nsec, Q-switched ruby laser beam onto a beryllium target in the presence of gas at various pressures ranging fron 2×10−1 to 3 Torr. High-speed streak and framing camera as well as a prism spectrograph have been used as diagnostic tools. Space-resolved spectra show, besides an intense continuum, Stark-broadened lines from Be I and Be II. The reinforced argon lines when moving off the Be target surface are probably due to a shock wave driven by the Be plasma acting as a piston. A simple theoretical model taking this mechanism into account is proposed. Calculated curves for the outer radius variations of the shock front fit closely the experimental results.