Low energy upscattering of UCN in interaction with the surface of solid state

In connection with the problem of anomalous losses of ultracold neutrons (UCN) in the storage in the material traps the measurements of quasi-elastic scattering of UCN in collisions with trap surface have been carried out. It was observed that the probability of quasi-elastic scattering of UCN from energy interval 0-77 neV to 90-200 neV is (2.2+/-0.2)10^-8 per collision therefore the process of quasi-elastic scattering can not explain the effect of anomalous losses which is on the level 310^-5.