Cavities Rydberg atom studies

The problem of the interaction between the electromagnetic field created due to the NSCE and various detectors (harmonic oscillators, two-level systems, Rydberg atoms, etc.) placed inside the cavity with moving walls was studied by different methods [188,189,234-238]. It is also discussed in this chapter. 

Ensembles of N Rydberg atoms prepared in the cavity also exhibit interesting effects. The atoms couple symmetrically to the field mode and collective radiative effects are observable even if the atomic sample is made of a few radiators only. Tests of superradiance theory and related radiative effects have been studied on these systems which-when N goes down to unity-constitute the smallest maser systems ever achieved. 

The Rydberg atom experiments described above are well adapted to the study of the atomic observables via the very sensitive field ionization method. The observation of the field itself and its fluctuations would also be very interesting. (In the Bloch vector model, the field variables are associated to the pendulum velocity whereas the atomic ones are related to its position). It has recently been shown either by full quantum mechanical calculations or by the Bloch vector semi-classical approach that if the system is initially triggered by a small external field impinging on the cavity, the fluctuations on one phase of the field become at some time smaller than in the vacuum field. This is a case of radiation "squeezing" which would be very interesting to study on Rydberg atom maser systems. 

While ionization by linearly polarized fields has been well studied, there is only one report of ionization by a circularly polarized field, the ionization of Na by an 8.5 GHz field.36 In the experiment Na atoms in an atomic beam pass through a Fabry-Perot microwave cavity, where they are excited to a Rydberg state using two pulsed tunable dye lasers tuned to the 3s — 3p and 3p —> Rydberg transitions at 5890 A and —4140 A respectively. The atoms are excited to the Rydberg states in the presence of the circularly polarized microwave field which is turned off 1 fis after the laser pulses. Immediately afterwards a pulsed field is applied to the atoms to drive any ions produced by microwave ionization to a microchannel plate detector. To measure the ionization threshold field the ion current is measured as the microwave power is varied. 

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