Comparison of EXAFS and LAXS Techniques

Bui there are further differences between the methods, which enn he seen by comparison of the integrands in equations (10.24) and (10.25). The atom pair correlation function in equation (10.24) is multiplied by expt 2i/a. ). which takes into account the effect of the liniie lifetime of the photo-electron and the hole generated by the absorption of the X-rays. Owing to the mean free path term expt--2r//.,). the pair correlation funciions are asymmetrical and damped with increasing distance. This effect can clearly be seen in ihe Fourier transform of the EXAFS function. 

Slow ly-varying tails of the pair correlation function contribute to FXAI- S data only at low k values. Sharp peaks in the pair correlation function. however, give rise to dominant features in the EXAFS signal which persist to high k values. As the data are Fourier transformed only in a liniie range and the low k data of the FXAI- S signal must he omitted in the Fourier transform. Ihe broad tail in the atom pair correlation function is ol ien lost in the analysis ol ihe li.XAF S dala. A 

Both methods provide pair correlation functions. but with different emphasis. X rax dillrac-tion is sensitive to the smooth behaviour ol the pair correlation function b.XAFS spectroscopv is more sensitive to sharp features of the pair eorre-hiliott function. Hence, the combination of both methods can give more complete and certain information. provided dtai the systems are not loo complex. 

Therefore, the lirst 30 years alter their discovery arc characterised by conlro ersial discussions 3I 40. particularly because only a restricted set 

These were discarded very soon, however, ami me now only of historic interest. Finally, the investigations of V. Sclilenk and VV. Schlenk led a crucial step further. They determined that the halogen ol certain Grigttard compounds can he completely removed as MgX, by precipitation with dioxane 40. Due to this information and new association data 39. they postulated the equilibrium  

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