Condition where the glancing angle for the incident X-rays is at or less than the critical angle and the X-rays are either reflected or absorbed in a region very close to the surface.
Note: The reflected intensity is close to \(\pu{100\%}\) of the incident intensity and the transmitted intensity is zero.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1849 (https://doi.org/10.1515/pac-2019-0404)