  Coherently manipulating Rydberg atoms in mesoscopic systems has proven
challenging due to the unwanted population of nearby Rydberg levels by
black-body radiation. Recently, there have been some efforts towards
understanding these effects using states with a low principal quantum number
that only have resonant dipole-dipole interactions. We perform experiments that
exhibit black-body-induced dipole-dipole interactions for a state that also has
a significant van der Waals interaction. Using an enhanced rate-equation model
that captures some of the long-range properties of the dipolar interaction, we
show that the initial degree of Rydberg excitation is dominated by the van der
Waals interaction, while the observed linewidth at later times is dominated by
the dipole-dipole interaction. We also point out some prospects for quantum
simulation.
