NIST Physical Measurement Laboratory X-Ray Form Factor, Attenuation, and Scattering Tables Main Page

[skip navigation] National Institute of Standards and Technology NIST Physical Measurement Laboratory

9. Results for Hydrogen and Helium

Hydrogen and helium serve as another example or extension since the general Cromer-Liberman approach did not apply to these two elements [17-20]. The form is however, simple, adapted in part from McMaster et al. [35]. The main difference between the (plotted) synthesis of Henke et al. [15,16] and the current form lies in the range and precision of the computation, the location of edge energies, the effective number of electrons assumed, and the interaction with scattering data. In all these respects, the current tabulation appears superior as a statement of atomic form factors.

However, use of atomic form factors in compounds or solids, particularly for hydrogen, involves significant shifts and potential structure not contained in these plots or tables. These chemical shifts and bonding redistributions serve as a caveat on use of the lower energy data (unless gaseous atomic hydrogen is used). Nonetheless, the data is able to represent a good approximation in general cases.

Back to Main Page
Table of Contents - 1995
previous page next page