Detection of Rydberg atoms

Techniques where the laser excites the atoms but the ionizing step is performed by field ionization have found increasing applications in the detection of Rydberg atoms in atomic beams (Sect. 9.6), in analytical chemistry for trace elements, or for small concentrations of pollutants [92]. 

Fig. 5.25 Selective detection of Rydberg atoms in specific Rydberg states...

Fig. 2.10. Experimental set-up used by Fabre et al. for the observation of the transmission of Rydberg atoms through a mechanical grating. Rydberg atoms impinge on a gold foil (a) which contains the array of micrometre-size slits. A set (b) of large holes is used for calibration, and a movable shutter uncovers either (a) or (b). The transmitted atoms are detected by field ionisation, using a pulsed voltage V(t) applied to a pair of parallel plates, which ionises the atoms and sweeps them into an electron multiplier (EM) (after C. Fabre et al. [37]).

On the other hand, the large dipole moment of Rydberg atoms offers the possibility to use them as sensitive detectors for microwave and submillimeter-wave radiation [566]. For the detection of radiation with frequency to, a Rydberg level n) is selectively excited by stepwise excitation with lasers in an external electric dc field. The field strength is adjusted in such a way that the energy En of the Rydberg level n) is just below the critical value Eq for field ionization, but E -i- hco is just above. Every absorbed microwave photon tuo then produces an ion that can be detected with 100 % efficiency (Fig. 5.26). 

Figure 23.16 Schematic view of the Rydberg tagging technique for the study of the elementary chemical reaction involving the detection of H atoms. Adapted from Schnieder et ai, J. Chem. Phys., 1997, 107 6175, with permission of the American Institute of Physics...

Further experimental studies concern microwave superradiance. It is interesting to mention that blackbody radiation rather than spontaneous emission initiates superradiance and maser activity in the systems described above. Using a beam of Rydberg atoms Ducas et detected far-infrared... 

T. P. Softley The aims of ZEKE spectroscopy are conceptually different from the atomic pulsed-field ionization experiments that predate ZEKE. In the latter, the aim is always to observe and study the individual Rydberg states. In ZEKE spectroscopy the aim is to detect small batches of Rydberg states lying below successive vibration-rotation thresholds of the ion without specific interest in the individual Ryd-... 

While Rydberg atoms have been used to detect infrared radiation with wavelengths as short as 2.34 ftm, they are most effective as detectors of far infrared... 

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