Eric, Your statement below -
"it is true that the neutron-capture cross section goes way down when the neutrons are very slow." - is not strictly correct. Check the 'Atlas of Neutron Capture Cross Sections' web page at: http://nucleus.iaea.org/sso/NUCLEUS.html?exturl=http://www-nds.iaea.org/ngatlas2/ Click on, say, 'Ni' in the periodic table shown, then check the cross sections for various nickel isotopes. They can be thousands of 'barns' (i.e., the cross section of a uranium nucleus). Most Ni cross sections go up quickly as neutron kinetic energy declines. The statement that escaping neutrons should be found may be correct. However, the interaction of low energy neutrons with nanoparticles, or surfaces with nano-topography seems complicated, so I'm unsure. -- Lou Pagnucco Eric Walker wrote: > Ed Storms brings up an excellent point about neutron-based explanations. > Here is my elaboration: it is true that the neutron-capture cross > section > goes way down when the neutrons are very slow. But that's a relative > change of what is normally measured at higher energies, and even with a > hypothesized momentum near or at zero, the cross section will not be > infinite. So there will be some elastic collisions with atoms in the > environment, and some of the neutrons can be expected to thermalize and > exit the system. You would then expect to see a substantial number of > these be picked up in a detector, but this is not seen. > > Eric >
