Density functional theory of Rydberg matter

The phase transition to a condensed state in a system of excited atoms was theoretically investigated in the beginning of 80-s, it was found that such a transition exists and is energetically favorable. From the beginning of 90-s extensive experiments were performed on behavior of dense systems of e xcited Cs atoms. Long lived massive clusters made of excited Cs atoms were detected, measurements of Rydberg matter (RM) parameters were performed. Th eoretical description of RM is a complex task taking into account its excit ed nature and very inhomogeneous distribution of valence electrons. Direct application of DFT to RM lead to many complications. We suggested to use ps eudopotential conception for the description of excited atoms, then through formal replacement of excited atoms by ground state pseudoatoms, to apply DFT. This procedure was used for general formulation of RM theory. Paramete rs of RM made of highly excited Cs atoms were obtained on this basis. RM li fetime was estimated ibr both radiation and Auger processes, impurity recom bination was considered also. A very long lifetime was predicted decay proc esses being suppressed by spatial and energetically separation of valence e lectrons and inner shell recombination states. Comparison of theoretical es timations with experimental data showed satisfactory coincidence.