Direction correlation coefficients in compound nuclear reactionsA reply

This chapter reviews methods that depend on orienting nuclei along a direction fixed in the laboratory system. The spins and parities of atomic nuclei and their magnetic moments and electric quadrupole moments, are of great interest for testing and improving nuclear models, and a variety of methods have been evolved for their study. In the absence of external fields, the nuclear magnetic substates will all have the same energy and will be equally populated. This degeneracy may be partially lifted by the application of suitable electric or magnetic fields to the electric or magnetic multipole moment of the nucleus giving each magnetic substate M a different energy E(M). Apart from the application of external fields, there are a number of ways in which ionic and crystalline fields can be used. A number of methods are available for the detection of oriented nuclei. If the nuclei are radioactive, the angular distribution of the radiation, whether particle or electromagnetic, will depend on both the degree of orientation of the parent nuclei and the angular momenta involved in the transition. Thus, the detection of an anisotropic distribution of radiation demonstrates the existence of oriented nuclei.