Compound Particle-Core Coupled States and Direct Nuclear Processes

Abstract

Phys. Rev. B5, 3953 (1972). J1 In the spirit of the Stoner-Wohlfarth-Slater model, one anticipates exchange splitting of sufficient magnitude to produce the observed saturation magnetic moment. This should approximate the width of the density Recent measurements in the lead region have shown that many of the important structural features may be understood on the basis of a weakcoupling model (WCM) 1 and that study of isobaricanalog states (IAS) provides a powerful probe for study of such structure.We report herein on a study, both experimental and theoretical, of the 206 Pb(^,^,) 206 Pb*(2 1 + ) inelastic scattering interaction in the incident proton energy range from 14.2 to 17.3 MeV which spans a number of the well-known IAS in this mass region. We have found that, using wellestablished optical-model parameters for this region and the structural information on the IAS deduced from earlier direct deuteron stripping reaction studies, it has been possible to obtain rather remarkable quantitative reproduction of the experimental data over this entire energy region. Of particular interest has been the dominant role played by interference effects both between different IAS compound-resonance amplitudes and between these and the direct scattering amplitudes.The spreading of the single-particle strength in 207 Pb was initially investigated by Auerbach and Stein. 2 Their study, based on the coupling of the 2^9 /2, li'n/a, 3 <*5/ 2 > 45 i/2> 3d 3/2 , and 2g 1/2 single neutrons to the 0 X + ground state and the first 2 X + excited state of 206 Pb, showed that the WCM does predict all the gross features of the experimental of states peak in which the paramagnetic Fermi level falls, ~ 1.0 eV being the band-theory consensus. (See Ref. 10.) One then expects shifts of approximately J this amount for structure in the majority spin band as the temperature ranges through the Curie point. 12 C. S. Fadley and D. A. Shirley, Phys. Rev. A 2, 1109 (1970). 13 C. S. Fadley and E. P. Wohlfarth, Comments Solid State Phys. 4, 48 (1972).large-angle inelastic scattering excitation functions populating the 2/ state in 206 Pb(^£') 206 Pb* studies. Two prominent effects neglected in this, and numerous other analysis of reactions involving IAS, are the resonance-resonance (RR) interferences resulting from the often observed overlap of the analog states involved and the directresonance (DR) interference reflecting the mixing of the analog states with a nonresonant (NR) scattering background. While such neglect has reduced the complexity of the IAS analyses, it constitutes a major limitation in the detailed examination, and careful extraction, of nuclearstructure information.The theoretical methods 3 proposed for removing these limitations have stimulated us to study systematically the strong interference patterns of the 206 Pb(/>,/)') 206 Pb*(2 1 + ) angular distributions measured on and off resonance.Proton beams with incident laboratory energies between 14.2 and 17.3 MeV from the Yale MP tandem were used to bombard a self-supporting isotopi...