부산대학교 도서관

The nucleus 206 Pb differs from the doubly magic nucleus 208 Pb by two missing neutrons. In 208 Pb most states at E x < 7.4 MeV are described by one-particle one-hole configurations. The lowest configurations with a g 9 / 2 particle and dominant p 1 / 2 , f 5 / 2 , p 3 / 2 holes and admixtures from f 7 / 2 and a few more configurations build an ensemble of two dozen states at 3.2 < E x < 4.9 MeV. They are described by rather complete orthonormal transformation matrices of two dozen states with spins from 2 - to 8 - to configurations. In 206 Pb a similar ensemble of states is deduced from the analysis of angular distributions measured in 1969 for the 206 Pb (p , p ′) reaction via the g 9 / 2 IAR in 207 Bi . An equivalent 208 Pb (p , p ′) experiment was performed in 1968 at the Max–Planck–Institut für Kernphysik at Heidelberg (Germany). New spins are determined for 32 states and 22 levels in 206 Pb . The comparison to corresponding states in 208 Pb studied especially in 1982 yields both remarkable similarities and clear differences. Sizeable g 9 / 2 p 1 / 2 strength found in 4 - and 5 - states is interpreted as admixtures of p 3 / 2 - 2 and f 5 / 2 - 2 components to the ground state of 206 Pb with dominant p 1 / 2 - 2 character. The description of nuclear states by shell model particle-hole configurations in the lead region needs the inclusion of collective excitations at already very low excitation energies. For the two isotopes 206 Pb and 208 Pb a rather good agreement of excitation energies and configuration mixing is observed for states at 3.7 < E x < 4.7 MeV. [ABSTRACT FROM AUTHOR]