KJ3055-Chapter 8 (X Ray Spectrometry)

Sample penetration depth: effect on excitation and fluorescence

In XRF, excitation and emission conditions vary with the sample penetration depth (d). Due to absorption, the excitation beam intensity decreases with d (according to Lambert –Beer law) and renders the excitation less efficient at a higher d (Curve 1).

Fluorescence radiation is partially re-adsorbed in the sample before leaving it. That is why the amount of radiation arising from a longer d is smaller (Curve 2). The effect of the lower excitation intensity at a longer d adds to the re-adsorption effect and contributes to the decrease in fluorescence efficiency with the increase in d.

Such processes are dependent on matrix properties and should be corrected for.

Graph adapted from http://users.skynet.be/xray_corner/xrc/screenshot.html

F.G. Banica, 09-03-20