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We report on our recent experiments with an interacting cold Rydberg gas of strontium atoms. Atoms such as strontium that have two valence electrons provide a new approach for studying cold Rydberg gases. If one of the valence electrons is in a Rydberg state, then the remaining valence electron can be excited almost independently, providing a new "handle" for manipulating the Rydberg atoms.
In our current experiments we initially prepare the atoms in 5sns or 5snd Rydberg states by exciting atoms from a MOT. After some delay, a subsequent laser pulse excites the second electron, and the resulting e.g. 5pnd states rapidly autoionize. We show that the autoionization signal can be used as a state-selective probe of the evolution of the Rydberg gas. By measuring the autoionization spectrum as a function of the delay, we observe the formation of a plasma, and the resultant transfer of population to long-lived high-l Rydberg states. This technique can be extended to provide spatial as well as temporal information on the distribution of Rydberg atoms. |
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