Reflection coefficients and complete angular distributions have been measured at angles of incidence between normal and near grazing for thermal beams of RbI molecules which were scattered from clean and beam‐covered NaCl (100) surfaces. For fixed angles of incidence and scattering the intensity of scattered molecules was measured as a function of coverage of RbI on the sodium chloride surfaces. Dynamics of the gas‐surface interactions are discussed and a mechanism for condensation of RbI is proposed.