The angular distribution of phonons radiated from a heated solid surface into liquid4He. II. Cleaved sodium fluoride (100) faces

Abstract

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 0.9K1or 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.