For pt.I see ibid., vol.8, 289 (1975). Detailed measurements of the angular distribution of phonons radiated from the cleaved (100) faces of sodium fluoride crystals pulse heated to 0.9K<or approximately=T₁<or approximately=3.2K into ⁴He at T approximately 0.1K are presented for the first time. The angular distributions can be resolved into two components, a narrow central peak and a broad background, the shape of the central peak being explicable on a modified acoustic mismatch theory where surface damping in the solid is taken into account. The background component accounts for the majority (>or approximately=85%) of the energy flux across the interface at all source temperatures, and its variation with source temperature T₁ corresponds well to the temperature dependence of the excess Kapitza conductance observed in steady heat flow experiments for a wide variety of materials. This temperature dependence is consistent with a threshold energy for transmission into the background of approximately 5K.