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Starting with strontium atoms loaded into a MOT we create a gas of cold Rydberg atoms. We excite the ground state atoms to Rydberg states via a resonant two photon transition using narrowband CW lasers. Ions are spontaneously emitted from the cold Rydberg gas. This ionization is enhanced if the Rydberg atom density is high enough to form a cold plasma, and then very long lived ion signals are observed as the Rydberg atoms are transferred to high L states through Stark mixing.
An advantage of using an alkali-earth element like strontium is that there is still a core electron left that can be optically excited after the Rydberg excitation. Excitation of this electron leads to ionization of the Rydberg atom with a very high probability. This process is known as autoionization. We use autoionization as a high yield probe of the Rydberg state population. The evolution of the autoionizing resonance over time after the Rydberg excitation offers a direct indicator of transfer into high L states. |
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