THE STRUCTURE OF HEAVY NUCLEI: A STUDY OF VERY WEAK ALPHA BRANCHING

Abstract

Very weak alpha branching in heavy elem.entswas studied by a recently developed coincidence technique, This technique makes it possible to measure the energies and intensities of both a~particle groups and de~exciting radiation, even when the transition intensities are as low as 10~8 relative to the most intense alpha group.Twenty . 1 0 P 214 F 254 h b .d a-partlc e emltters rom 0to m ave een examIne , 00+ states ("beta vibrations ail were observed in six even-even nuclei, and analogous states were found in three odd~mass: nuclei.They are in general characterized by low alpha-decay hindrance factors and roughly equal de -excitation by electric monopole and quadrupble transitions.However, the de -excitation of these states is in disagreem ent with vibrational model predictions in certain cases; more important, the de-excitation and other properties of the states exhibit some irregular variations from nucleus to nucleus which are evidence 01' some particle character in the states.Information was also obtained about some other types of levels.A number of 1~states (i1octupole vibrations il~were observed, and a possible 2-state was observed in U 236 A state that a.ppears to be analogous to the 1=octupolestates of even-even nuclei was observed in U 235 .In Pu 239 , a K:= 3/2+[631] band was identified with reasonable certainty, and numerous particle states were observed in Bk 249 although it was not possible to dassHythern.No 22+ states (aagamma vibrations iI) were observed, and it appears that the alpha transitions to these states are rather highly retarded.