escape depth (for surface analysis techniques)
The distance into the sample measured from the physical surface from which all but a fraction \(\frac{1}{e}\) of the particles or radiation detected have originated.
PAC, 1979, 51, 2243. (General aspects of trace analytical methods—IV. Recommendations for nomenclature, standard procedures and reporting of experimental data for surface analysis techniques) on page 2247 [Terms] [Paper]