AVERAGE ATOMIC NUMBER
Also known as Z-bar or Mean Atomic Number (MAN). The sum of the elemental weight or atomic fractions of the element atomic numbers of a sample.
The sum of the weight fractions of the atomic numbers of a sample is applicable for modeling the background continuum and is used in the MAN background correction iterated polynomial calculation by Probe for EPMA to approximate the average z-bar (electron fractions are actually more rigorous).
On the other hand, the sum of the atomic fractions of the atomic numbers of a sample is applicable to stopping power calculations and is used in Monte Carlo calculations of electron trajectories.
The weight fraction calculation is quite simply :
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where
:
is the atomic number of the element
is the
elemental weight or atomic percent of the element