Positive parity states inPb208excited by the proton decay of the isobaric analog intruder resonancej15/2

Abstract

With the Q3D magnetic spectrograph of the Maier-Leibnitz-Laboratorium at München at a resolution of about 3 keV, angular distributions and excitation functions of the reaction 208 Pb(p,p ) were measured at some scattering angles 20 • -138 • for several proton energies 14.8-18.1 MeV. All seven known isobaric analog resonances in 209 Bi are covered. By the excitation near the j 15/2 intruder resonance in 209 Bi, several new positive parity states in 208 Pb with excitation energies 4.6-6.2 MeV are identified by comparison of the mean cross section to the known single particle widths. The dominant configuration for 27 positive parity states is determined and compared to the schematic shell model.

Identification of the0+proton pairing vibration state in the doubly magic nucleusPb208by particle spectroscopy

“…multiplet are identified, as well: the 5286 state as the 2+ member and the 5216 state as the 4+ member [18]. The 6+ member is mixed with the large number of particle-hole configurations; most of them but not all are identified [8].…”

“…Because of the double magicity, the level density in 208Pb is low. Below Ex = 3.9 MeV, there are only five states and at 3.9 ^ Ex < 5.8 MeV about 110 states are identified with certainty [1,[5][6][7][8][9][10][11][12][13][14][15], At Ex <5.8 MeV, the range of spins is from 1+ to 11+ and from 0" to 8A The mean number of states with the same spin and parity is between one and six by excepting the 11, 13, and 12 states with spins 3" , 4" , and 5" . Nevertheless because of the multitude of spins and the two parities, about one-third of the states have spacings less than 3 keV.…”

“…Among more than 300 known levels [1], most bound states are described by the shell model [2][3][4] with one-particle one-hole configurations [1,[5][6][7][8][9][10][11][12][13][14][15][16]]. …”

“…Prerequisites are the good precision and the high sensitivity of the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium (MLL Garching, Germany) [29,30] which al lowed to identify most states below 8 MeV in 208Pb with cross sections varying from less than 1 to nearly 1000jub/sr [5][6][7][8][9][10][11][12][13][14][15]. Excitation energies are determined with uncertainties of typically 0.5 keV, but down to 10 eV for isolated and strongly excited states.…”

“…Ill C 1). Indeed, a resolution of 1.5 keV half-width at half-maximum on the low energy side is obtained with the Q3D magnetic spectrograph at the MLL (Garching, Germany) [8], …”