Hanle effect superpositional

Fig. 4.11. Hanle effect on the degree of linear polarization V = (/y — Iff/(I + Iff) at (P, f )-excitation 1 - superpositional signal calculated at the same conditions as Fig. 4.10, dots refer to the positions a, b, c, d as in Fig. 4.10 2 - pure excited state signal at x = 0 3 - pure ground state signal at gj> = 0 4 - experimentally measured dependence for Te2 under conditions as given in Fig. 4.6, curve 1, but in the region of weaker magnetic field and at strong pumping (x 3).

Fig. 4.11 reflects a superpositional Hanle effect from both the ground (initial) and excited states. To demonstrate this in Fig. 4.11 we depict the pure ground state effect (supposing gj> = 0) (see curve 3), as well as the pure excited state effect (supposing = 0) (see curve 2). In this favorable situation both effects are well distinguished in the observable superpositional signal. 

The superpositional Hanle effect may lead to some, at first glance, unexpected peculiarities. Firstly we wish to draw attention to one interesting fact [17] under conditions where the effect has already developed from the ground state (ujj"/jk S> 1), but that from the excited state... 

Note that the superpositional Hanle signal, reflecting overlapping of effects from both levels, coupled with optical excitation, is sensitive to the signs of the Lande factors gj> and gj even with Lorentzian geometry, where

linear Hanle effect. This is easily understood, since there is a large difference between the cases... 

This formula describes the signal around zero magnetic field, the so-called Hanle effect. The signal is generally a superposition of a Lorentzian... 

This formula describes the signal around zero magnetic field, the so-called Hanle effect. The signal is generally a superposition of a Lorentzian and a dispersion curve on a constant background. The background corresponds to the incoherent excitation processes, in which each level scatters individually. We note that... 

These experiments are in fact entirely analagous to the Hanle effect or zero-field level-crossing experiments involving excited atoms discussed in Chapter 15. The coherent polarization of the pumping light referred to the quantization axis Oz in Fig.17.12 prepares the atoms in a coherent superposition of ground-state Zeeman sub-levels. The ensemble density matrix now has finite off-diagonal elements... 

The iodine molecule has been very thoroughly studied with electric and magnetic level-crossing spectroscopy. The hyperfine structure of the rotational levels affects the profile of the level-crossing curves [849]. A computer fit to the non-Lorentzian superposition of all Hanle curves from the different hfs levels allows simultaneous determination of the Landd factor g and the lifetime t [850]. Because of different predissociation rates the effective lifetimes of different hfs levels differ considerably. 

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