  The spatial evolution of the Rydberg blockade is studied taking into account
Stark-split energy levels across several manifolds. We find that the unexpected
restoration of a blockaded Rydberg excitation at small interatomic distances,
e.g., experimentally observed by P.Schauss, et al. [Nature 491, 87 (2012)], can
be explained by the perturbed energy levels from neighboring manifolds that
enter the energy window of excitation defined by the bandwidth of the exciting
laser. The same mechanism can also explain why the pair correlation function of
Rydberg atoms remains nonzero in the entire region of Rydberg blockade.
