Adiabatic stabilization: Observation of the surviving population

Photoionization of the circular 5g Rydberg state in neon by an intense subpicosecond light pulse is studied. Both the photoionization yield and the remaining population are measured. We find that the photoionization yield does not increase when the pulse peak intensity is increased above 60 TW/${\mathrm{cm}}^2$, and that a large fraction of the population remains in the 5g state instead. These results are consistent with predictions for adiabatic stabilization. The measurements are done using a sequence of three laser pulses. The first laser pulse excites the circular 5g state from the neon ground state, the second pulse is the intense light pulse that leads to the ionization (or lack thereof due to stabilization) we actually study, and the third pulse is a low-intensity high-fluence pulse ionizing all of the remaining 5g population. The photoionization yields of these three pulses are detected and separated by electron spectroscopy.