Spectroscopy on Collimated Atomic Beams

As we have already noted (Sect.6.1.1), a well-collimated atomic beam displays a very small absorption width perpendicular to the atomic beam. As shown in Fig.9.35, the collimation ratio C for an atomic beam is defined as 

The residual (first-order) Doppler broadening mated atomic beam is given by 

The atomic beam technique is a very versatile one. Atomic beams can be produced for essentially any element, whereas conventional cell techniques are limited to a temperature interval up to about 1000° C. Besides reducing the Doppler width, collisional effects are significantly reduced with the atomic-beam technique compared with cells. The possibility of utilizing spatially separated interaction regions along the beam is also valuable in certain cases. We note that the most probable velocity v of a thermal atomic beam emerging from an oven is 

As can be seen from the inserted experimental curve, such a linewidth can be approached. In Fig. 9.38 a further example of this type of spectroscopy is given. Here a broadband cw laser has been used to populate the rather long-lived 5d (r-l zs) state in in the cascade decay of the 

An example of the Stark effect is given in Fig.9.39. Note, that while only the tensor Stark interaction constant 03 (Sect.2.5.2) can be determined in an LC experiment (Sect.7.1.5 Fig.9.18), the scalar interaction constant ag can be obtained in this type of experiment as well as 03. In the same way, isotope shifts can be measured by direct optical high-resolution methods while resonance methods and quantum-beat spectroscopy can only be used for measurements of splittings within the same atom. 

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We will first describe spectroscopy on collimated atomic beams and on kinematically compressed ion beams. Two groups of nonlinear spectroscopic techniques will be discussed saturation techniques and two-photon absorp-... 

We will first describe spectroscopy on collimated atomic beams and on kinematically compressed ion beams. Two groups of nonlinear spectroscopic tecliniques will be discussed saturation techniques and two-photon absorption techniques. We will also deal with the optical analogy to the Ramsey fringe technique (Sect. 7.1.2). In a subsequent section (Sect. 9.8) laser cooling and atom- and ion-trap techniques will be discussed. Here, the particles are basically brought to rest, ehminating the Doppler as well as the transit broadening effects. 

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