This book presents the first study on the radiative relaxation mechanism of water between its different phases in order to explain an uncommon radiation phenomenon observed in the first-order phase-transition process of water. This kind of radiation is often referred to as phase-transition radiation, whose nature is different from the Planckian radiation because its strength can be even stronger than blackbody radiation at the same temperature. Changes of energetic behaviors of water molecules during phase transitions are linked to the direct emission of infrared radiation. The reported...