depth resolution

The distance between the 84 and 16 per cent levels of the depth profile of an element in a perfect sandwich sample with an infinitesimally small overlap of the components. These limits correspond to the 2 $Math - text$ -value of the Gaussian distribution of the signal at the interface.

Source:

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