High resolution particle spectroscopy in 208Pb

By using the Q3D magnetic spectrograph of the Maier-Leibnitz-Laboratorium at Munchen, particle-hole states in Pb-208 are investigated. With the reaction Pb-208(p, p') at energies 14 < E-p < 18MeV an instrumental resolution of delta E-p'/E-p' = 3 . 10(-4) is achieved for protons without energy loss in the target. For lower energies E-p' an exponential tail with a width proportional to the effective target thickness appears. Below E-x = 8.2 MeV more than 250 states in Pb-208 are observed. Excitation energies are derived with uncertainties of 0.1 keV for strongly excited states by calibration with known data from Nuclear Data Sheets. Pb-208(p, p') via isobaric analog resonances (IAR) in Bi-209 allows to determine the neutron particle-hole components of each state in Pb-208. The selective excitation in an IAR yields the parity for each state. Spin and dominant neutron particle-hole configurations of a state are determined from the mean cross section and the shape of the angular distribution for Pb-208(p, p'). From about 120 particle-hole states predicted by the shell model in Pb-208 below E-x = 6.1 MeV, about 50 states with negative parity and 30 states with positive parity are identified.