Discovery of collective states in 208Pb by complete spectroscopy

Andreas Heusler,G De Angelis,L Corradi

doi:10.1051/epjconf/201922301023

Abstract

Most neutron and proton bound states in 208Pb are described in the shell model as one-particle onehole configurations. Besides precise data obtained with the Q3D magnetic spectrograph of the MLL (Garching, Germany) an important reaction is the inelastic proton scattering via isobaric analog resonances in 209Bi. It yields amplitudes of neutron one-particle one-hole configurations with relative signs in each stateof 208Pb. The orthogonality, normality, and sum rule relations allow to investigate the completeness of the transformation matrices of one-particle one-hole configurations describing the states in 208Pb with spins from 0− to 14− and 0+ to 12+. By this method amplitudes of unobservable one-particle one-hole configurations can be determined.The comparison of spin, parity, and dominant particle-hole components thus derived in up to 30 states of a certain spin to shell model calculations allows to identify states described as collective excitations of the entire nucleus.

Highlights

208Pb is the heaviest nucleus where more than 500 states are rather well known [1]
Complete spectroscopy allows to find collective states in the heavy nucleus 208Pb not described as 1p1h configurations
Complete spectroscopy is approached by studying several different reactions, especially 208Pb(p, p′), 208Pb(d, d′), 208Pb(α, α′), 207Pb(d, p) and 209Bi(d, 3He)

Summary

Introduction

The excitation energies of most neutron bound states (S (n) = 7368 keV) and part of the proton bound states (S (n) = 8004 keV) are known with an uncertainty of less than 1 keV. Parity, and dominant configuration up to a certain excitation energy defines complete spectroscopy. It is rather good for states at Ex < 7.2 MeV. States at Ex < 6.2 MeV are completely known with spin, parity, and dominant configuration [3]. Complete spectroscopy allows to find collective states in the heavy nucleus 208Pb not described as 1p1h configurations

Experimental observations

Complete spectroscopy

Summary

Outlook