I think using synchrotron radiation XAFS is definitely better than lab XAFS, but now the test results of lab XAFS are comparable to those of synchrotron radiation sources. In the future, can laboratory XAFS really replace synchrotron radiation XAFS? Is the lab XAFS up to the task when testing low concentration samples? At present, I am considering doing XAFS test, thinking that XAFS in the laboratory is more affordable, but I don't know how the test effect will be.
Dear Long He ,
it is long time ago since I have done EXAFS (end of 1970's).
First I started with EXAFS doing at a conventional x-ray tube system but also have done EXAFS experiments at a synchrotron in photo electron detection mode ('old' DESY itself).
Even at that time the x-ray tube EXAFS experiments already revealed results of same quality as the synchrotron experiments.
The outstanding advantage of synchrotron experiments is that you are able to utilize the high x-ray photon flux; so one is able to do investigations with respect to a) diluted systems ('testing low concentration samples' as already mentioned above) and b) time resolved XAFS ( e.g. QEXAFS).
However in the synchrotron case one has to grapple*) with the time structure of the photon flux such as pulsed x-ray bunches with quite low duty cycle and a continously decreasing photon flux due to the decay of the electron beam intensity. During the restoring time interval of the synchrotron's electron current one is not able to do the experiments.
In contrast to that the x-ray photon flux of a conventional x-ray tube set up ('laboratory XAFS') does not show such time issues.
Another 'advantage' of the synchrotron radiation is the quite 'parallel' primary beam compared to that of an x-ray tube; a property, which can help to prevent intensity losses when larger distances are involved in the experimental set-up.
*) in the mean time one has learned how to deal with these issues...
Best regards
G.M.
Synchrotron based XAFS is and probably will be the golden standard, unless somebody figures out an inexpensive way to produce orders of magnitude more photons in the lab setting than what can be done with the x-ray tubes.
However, there are lots of applications where a lab-based instrument can already be better than the synchrotron. For example, if you want to characterize the result of a chemical synthesis, a lab instrument can give the needed information cheaper and with better accessibility. Also running very long experiments (~weeks) is only possible with a lab instrument.
Low brilliance can be a problem though. In my former lab, I did manage to measure Se XANES spectrum from kale leaves with an estimated concentration of ~50mg/kg but it wasn't easy and took days of collection time (https://www.researchgate.net/publication/335156880_The_reduction_of_seleniumIV_by_boreal_Pseudomonas_sp_strain_T5-6-I_-_Effects_on_seleniumIV_uptake_in_Brassica_oleracea).
Later they've used the same but upgraded instrument to measure CuO thin films down to 14 nm thickness. XANES spectra could be measured in tens of minutes and EXAFS in a few days. (https://www.researchgate.net/publication/365645974_Laboratory-scale_x-ray_absorption_spectroscopy_of_3d_transition_metals_in_inorganic_thin_films)
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