Surface matter waves caused by the absorption of nonrelativistic particles

Abstract

The existence of surface states of nonrelativistic particles at the interface between a vacuum and a layer of a material on a reflecting substrate, which are caused by the absorption in the layer rather than the presence of discrete levels, is established. The wave functions of such states (surface matter waves) are found and the domains of their existence in the complex plane of the “optical” potential (both attractive and repulsive) of the layer are determined. Threshold effects of the count of microparticles at the intersection of the boundaries of these domains are revealed. The spatial characteristics of the surface matter waves are calculated. An example of the layer composition providing the existence of such waves is given for ultracold neutrons. The increase in the loss of trapped ultracold neutrons owing to the excitation of the surface matter waves of these particles in the trap walls is discussed.