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We have used photostimulated flash luminescence to study deep electronic states arising when silver ions Ag + are deposited under high vacuum onto the surface of a ZnS single crystal, followed by creation of the conditions for neutralization of the silver ions. The flux density of the silver ion beam was 10 7 cm -2 ⋅sec -1 . We have observed the appearance of two types of deep electronic states with photoionization energies 1.60 eV and 1.80 eV, arising after depositing the silver ions onto the surface of the ZnS single crystal. We have hypothesized that there may be two different preferred sites for adsorption of silver atoms on the zinc sulfide surface. The corresponding photoionization spectra of the adsorbed silver atoms have maxima at 775 nm and 690 nm.Key words: adsorbed silver atom, zinc sulfide, photoionization spectrum, photostimulated flash luminescence. Introduction.Today there is considerable interest in development of modern methods and principles for making nanoparticles and nanostructures. Such problems are relatively easy to solve, for example, for molecules when their capacity for self-organization is utilized, and for small atomic clusters and nanoparticles that can be prepared during chemical synthesis and incorporated into foreign matrices and porous structures [1][2][3][4][5]. A number of papers (see, for example, [6-8]) demonstrate the possibility of sequential photostimulated assembly of adsorbed nanoparticles from atoms and small atomic clusters. During such investigations, there are problems involved in obtaining individual, noninteracting atoms and monodisperse small atomic clusters adsorbed on the surface of real ionic/covalent crystals. However, so far in most cases the optical and other properties are still unknown for atoms and small atomic clusters of a strictly determined size that are adsorbed on the surface of crystals. Such problems can be solved only when these centers are present on the real crystal surface in concentrations ruling out their pairwise interaction and their joining into systems of another size, and making up at least 10 -3 to 10 -6 of the monolayer. However, sometimes it is simply impossible to observe such low concentrations of adsorbed centers using standard procedures. Some success has been achieved by using luminescence techniques such as photostimulated flash luminescence, for example [9,10]. Such problems have been successfully solved for atoms and clusters of a metal by itself, in particular silver on the surface of silver chloride [11,12]. This work has been devoted to studies of the spectral properties of individual silver atoms adsorbed on the surface of a ZnS crystal. We have not encountered similar research in the scientific literature. We also know that deep electronic states appear upon adsorption of silver particles of atomic or molecular dispersity on the surface of zinc sulfide crystals [13]. The practical use of such deep electron traps is certainly promising (see, for example, [14]).We obtained the photoionization spectra of adsorbed silver ato...