Reflected EXAFS ( REFLEXAFS )

Using an optically flat (i.e. flat on a near atomic scale) surface, EXAFS can be obtained by keeping the sample tilted at an angle to the X-ray beam which is less than the critical angle. The incident beam is reflected off the sample and EXAFS (see XAFS) spectra can be collected that have a high degree of surface sensitivity. The penetration depth is ca 50 Å.

As the angle used is normally in the range 0.1 to 0.2 degrees, the sample should be as long as possible so that an X-ray beam of reasonable vertical size (50-100 microns) can be used. Normally REFLEXAFS itself is not carried out by analysing the reflected intensity as this can be very tricky, but the fluorescence signal is collected which is why the technique is sometimes called fluorescence

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