Features of ultracold neutron capture in thin absorbing films

The dependence of the ultracold neutrons capture cross section in the thin targets as compared to the neutron wave length is calculated within the frames of the time quantum theory. It is shown, that by the tendency of the neutron velocity to the zero the neutron wave length tends to the infinity and the interaction volume becomes infinitely large consequently the capture cross section by the neutron low velocities constitutes σc ∼ ν, i.e. it tends to the zero by the neutron velocity value ν tendency to the zero