Femtosecond beats in the blue fluorescence of rubidium atoms

Summary form only given. The coherent control of processes involving photoexcitation of atoms and molecules has seen many interesting developments. In these studies the main goal is to control the outcome of a certain process by the interference between different quantum paths, and it has been explored in resonant one- and two-photon excitation of atoms. Also, some studies about propagation effects indicate that it is interesting to consider the influence of high optical densities in the coherent control of sequential two-photon absorption processes when an intermediate level resonance occurs. We present results of preparing an atomic wave packet which generates a field that strongly reacts back on the atomic system. The experiment is done in rubidium vapor, where the laser, with 1OO fs and tuned to 778 nm, is double resonant with the sequential atomic transitions 5S-5P/sub 3/2/-5D. Femtosecond and picosecond beats are observed by monitoring the time-integrated emission at 420 nm in a second cascade, 5D-6P/sub 3/2/-5S. The sample is excited by pairs of collinear femtosecond pulses with variable relative delay, which can be scanned at slow or fast rates.