fireball arises in this regisa and is caused by the radiative recombination of electrons and ateaic ions such as N7 +e eM - bv. about 10 msec. Recombination tise L: Since apprasiaately one-half of the total seposited enerzy i contained in the core Tegiou, covilng time for the fireball is sf che erder of the recombination tice. In addition to recombization radiation from the core, there is same radiation caused by free-free (Breusstrablung) electron interactions in the field of che atoms of the core and sooe line emission from excited atoms. Got bomb materials will also contribute in some degree to radiation froa thi region. Absorption of some of the radiation from the core in the outer "“polecular™ region gradually fsochermalizes the fireball so that at about § msec the fireball is an approxinate isotheraal sphere of about 20,000 feet radius. The temperature at this time is about 10,000 degrees K. Because ai at this temperature and pressure is quite transparent, ¢ the fnner portion of the firebsll is observable, and the cooling rate decreases markedly. This energy is absorbed in a lar region around the burst by photodissociation of oxygen molecules. Since re- cocbination of neutral atoms to form molecules requires three body collision which are extremely rare at Teac altitude, dissociation of 0, is essentially persarent, and this energy of the bomb is effectively wasted. 11.3 INSTSLEMENTATION As previously stated, quantities to be measured for the Teak and Orange everts were: (1) absolute surface brightness in three narrow spectral bands,