The report is of an informational and educational nature and was prepared based on materials from published works. The phenomenon of the neutron energy levels existence in the gravitational field above the mirror was predicted in [1]. Later, their existence was confirmed in experiment [2]. Further research was aimed at improving the accuracy of the experiment and finding the possibility of using this phenomenon. As a result, a high-precision method of ultracold neutron (UCN) spectrometry arise, based on measuring the frequency of neutron transition between energy levels [3]. UCN resonance gravity spectrometry can be applied to a number of fundamental studies, such as the search for new types of interactions, testing Einstein’s weak equivalence principle, and testing models of the dark matter and the dark energy. The experimental implementation of the method showed a record accuracy in measuring neutron energy at a level of 10-15 neV.

1. V.I. Luschikov and A.I. Frank, Quantum effects occurring when ultracold neutrons are stored on a plane, Pis’ma Zh. Eksp. Teor. Fiz., 20, 9, 607 (1978).
2. V.V. Nesvizhevsky, et al., Quantum states of neutrons in the Earth’s gravitational field, Nature, 415, 297 (2002).
3. H.Abele, et. al., Ramsey’s method of separated oscillating fields and its application to gravitationally induced quantum phase shifts, Phys. Rev. D, 81, 065019 (2010).