Level-band problem and many-body effects in cold Rydberg atoms

Recent experiments with cold Rydberg atoms are analyzed in the framework of a level-band model. Statistics of coupling between the level and the band and the band density of states resulting from the 1/R-3 interaction among t he atoms are found. It turns out that strong and weak; coupling are equally important, and therefore the population dynamics of such a system is diffe rent from the decay to a continuum. Returns of the population to the initia l state affect strongly the lineshapes of resonances. (C) 1999 Elsevier Sci ence B.V. All rights reserved.