Paschen-Back states

Paschen-Back states indicated in Figure IV-3 are excluded by the exclusion principle. For example, the electrons cannot both have m, = + and m = +1 this is an excluded state. The allowed states for two equivalent p electrons are seen by inspection to be 15 in number they are listed in Table IV-1. Note that these allowed states require that the quantum numbers to, and rnj, for the first electron be not identical with to, and mi, for the second electron moreover, two assignments of quantum numbers that differ only in the interchange of the two electrons are not counted as two states, but only as one. 

Although all the examples chosen involve singlet states, for which the theory is especially simple, there is no problem in extending the method to more complex Zeeman patterns, or indeed in including the effect of Paschen-Back uncoupling on the MOV spectrum [166]. The influence of -mixing on MOV patterns has also been studied, and is in principle well understood [167], If the experiment is performed with lasers, the influence of laser power on Faraday rotation arises both by population transfer and by the Autler-Townes splitting (section 9.10) [173]. 

Fig. 1 Level scheme of Na for ground and first excited state in Paschen-Back notation.

Fig.7.11. Optical double-resonance signals in the Paschen-Back region for excited S states of (1=3/2). Stepwise excitations from the ground 4 S /2 i/2... 

Electron-Nuclear Double-Resonance. In the ENDOR method NMR and ESR are combined. The technique is illustrated in Fig. 7.23, in wliich a system with S — 1/2 and J = 1/2 is considered. In the Paschen-Back region we have two mj values for each ms value. If a microwave field satiu ates the ESR transition between the states with mi = +1/2, only a weak absorption signal is obtained when an equilibrium situation is reached. The upper level... 

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