AVERAGE ATOMIC NUMBER

EPMA Probe

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 :

         

 

 

 

where :                         is the atomic number of the element

                         is the elemental weight or atomic percent of the element