L'orientation nucléaire à basse température et ses applications

A number of methods of orienting nuclei have been conceived so far. They lead either to polarization or to alinement. Two of them have already lead to successful experiments. They both obtain orientation through magnetic H. F. S. fields in paramagnetic substances. Radioactive nuclei oriented in this way show anisotropic emission of γ rays. A study of the anisotropy allows the multipole character of the γ ray transition to be determined. The determination of the plane of polarization makes a distinction between magnetic and electric multipoles possible. In certain cases one can also determine the character of a β ray transition preceeding the emission of γ rays. Future possibilities are discussed