Nuclear orientation as a tool for studying the structure of very unstable nuclei

With the availability of modern isotope separator on-line systems it has become possible to make broad and systematic studies of low-energy low-spin nuclear structure. A vital ingredient in such a program is unique spin-parity assignments to all low-lying levels. A most desirable complement to spin-parity information is detailed spectroscopic information. Obtaining such information far from stability is difficult because of low activity production. Nuclear orientation provides a means for obtaining spin assignments usingsingles measurements. This is less demanding on source intensities than - angular correlation coincidence measurements. Further, nuclear orientation can provide information on magnetic moments and on multipole mixing ratios. A number of structural problems are discussed: the need for unique spin assignments in systematics schemes; the need to distinguish between E2+E0 and M1 transitions; the importance of measuring E2-M1 mixing ratios; and the value of magnetic moment information. Particular emphasis is placed on the desirability of obtaining such information in the neutron-deficient Pt, Au, Hg, Tl, Pb and Bi isotopes, based upon the experimental program at the UNISOR facility.Work supported in part by U.S.Dept. of Energy, Contract No. DE-AS05-80ER10599.