Rabi apparatus

Nonoptical methods can be used to probe ground and metastable excited states as well as short-lived levels. One of these techniques, for example, utilizes the backward part, i.e., the B magnet of a classical Rabi apparatus, to deflect molecules after laser excitation and interaction with the rf field, and leaves the other particles unaffected, or vice versa. Another method, which has been applied rather frequently since it provides a high sensitivity, is the detection of ions or photoelectrons after state selective ionization of atoms or molecules. This can be accomplished by photoionization or by field ionization, where the latter applies particularly well to very highly excited states, i.e., to Rydberg atoms. 

NMR transitions were first observed by Rabi and co-workers in 1938, using a molecular-beam apparatus.3 NMR transitions in bulk matter were first detected in 1945 by two independent groups, one headed by Bloch, the other by Purcell these two men shared the 1952 Nobel physics prize.4... 

In writing about molecular beams, Otto Stem once referred to that beauty and peculiar charm which so firmly captivates physicists working in this field. Stern s statement accurately described Rabi s reaction to his experience in Hamburg. Rabi s powerful physical intuition was stimulated by images of atoms moving through the apparatus and once he was exposed to that beauty and peculiar charm, the course of Rabi s professional life was determined (see Figure 12.1). 

In 1950, Norman Ramsey, a member of the team that developed the magnetic resonance method, made a basic modification to Rabi s molecular beam apparatus that significantly enhanced... 

Following WWII, Rabi and I returned to Columbia, Lamb remained there and we were later joined by Kusch. Research resumed quickly. Harold K. Hughes [7] succeeded in making the first resonance apparatus with electric oscillating and deflecting fields and used it to study CsF. Nierenberg revived the old alkali resonance apparatus to study atomic cesium for his thesis. 

Fig. 9.53 Rabi molecular beam apparatus with Ramsey s separated fields...

Finally, optical pumping and double resonance have opened the way to experiments where the species under study can be confined in closed resonance cells, whereas Rabi s technique relied on the spatial separation of atoms or molecules in a beam arrangement. Also, the new methods allowed the investigation of ions that cannot be studied with a Rabi-type apparatus. 

The combination of electron-impact excitation with the laser version of the Rabi technique allows measurements of hfs splittings in higher excited states. Penselin and coworkers [10.23,24] have developed the atomic beam RF resonance apparatus shown in Fig. 10.10. Metals with a high condensa-... 

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