Microscopy and Microanalysis


Compositional Averaging of Continuum Intensities in Multielement Compounds

John J.  Donovan  a1 c1 and Nicholas E.  Pingitore  Jr. a2
a1 Department of Earth and Planetary Science, The University of California, Berkeley, CA 94720-4767, USA
a2 Department of Geological Sciences, The University of Texas at El Paso, El Paso, Texas 79968-0555, USA


We find no physical basis for traditional mass-fraction weighted averaging of X-ray continuum measured in pure elements to estimate continuum production from compounds. Measurements of continuum from pairs of stable isotopes demonstrate that mass alone (the presence of more or fewer neutrons) has no effect on continuum production in electron probe microanalysis. Electron-fraction weighted averaging, which is based on the relative contribution of each constituent element to the electron (or proton) composition of a compound, proved superior to mass-fraction weighted averaging, in predicting the continuum of a compound from the measured continuum of its elements.

(Received April 23 2001)
(Accepted November 27 2001)

Key Words: atomic fraction; atomic number averaging; average atomic number; bremsstrahlung; electron fraction; mass averaging; mass fraction; mean atomic number; X-ray continuum; z-bar.

c1 Corresponding author. E-mail: jdonovan@socrates.berkeley.edu