Energy-dependent neutron cross section data Where I can find a table with energy dependent cross sections for neutrons?
 A: Neutron-matter interaction cross-sections vary somewhat depending on the material in question, and depends greatly on energy. In addition, the type of neutron-matter interaction that statistically dominates depends on the energy, with elastic collision being the sole contributor to material cross-sections below energies of 4 MeV:

If you're talking about elastic scattering, another thing to note is that protons are really good at thermalizing neutrons via elastic interaction, a fact which owes primarily to the fact that neutrons and protons have similar masses. In contrast, scattering by larger atomic nuclei results in less effective thermalization:

A good approximate parametrization of the neutron-hydrogen elastic cross-section in units of barns is given by $$\sigma(E)=\frac{3 \pi }{(0.13 E+0.4223)^2+1.206 E},$$
as shown here:

The slides are taken from Wolf-Udo Schroeder's PHY466 notes at University of Rochester.
A: A good place to start is the National Nuclear Data Center's "Sigma" database.  The web interface is much improved since the time this question was asked.
