Interaction of ultracold neutrons with some gases

Cross sections calculation of interactions of ultracold neutrons (UCN) with molecules of H2, D2 para- and ortho-H2 and D2, N2, O2 and air in dependence on UCN velocity and gase temperature is carried out. The results of the calculations are compared with experiment. It is shown that elastic scattering cross-section (σsub(e)) is not dependent on UCN velocity (Vsub(UCN)), but inelastic scattering cross-section (σsub(in)) obeys the law of 1/Vsub(UCN) and is in agreement with limiting conclusions of the quantum scattering theory. An account of molecule velocity distribution results in the 1/Vsub(UCN) dependence of scattering cross-section as a function of velocity. In this case, cross-sections of inelastic processes stay constant, and cross-sections of elastic processes grow to a value about /Vsub(UCN), where is a mean thermal molecule velocity