"Atom Scattering Factor" is measure of the scattering power of an isolated atom.
Applicable units are those of quantitykind:AtomScatteringFactor
http://reference.iucr.org/dictionary/Atomic_scattering_factor
"Atom Scattering Factor" is measure of the scattering power of an isolated atom.
$f = \frac{E_a}{E_e}$, where $E_a$ is the radiation amplitude scattered by the atom and $E_e$ is the radiation ampliture scattered by a single electron.
http://www.iso.org/iso/catalogue_detail?csnumber=31897