Identification of the 0+ proton pairing vibration state in the doubly magic nucleus 208Pb by particle spectroscopy

Among about 150 levels below E-x = 5.86 MeV in Pb-208 listed by the Nuclear Data Sheets as of 2007, most levels were recently identified as particle-hole states. All natural parity states excited by the Pb-208(alpha, alpha') reaction are identified, two of them are newly identified. The state at E-x = 5667 keV is identified as the 0(+) proton pairing vibration state. Based on the analysis of data from the Pb-206,Pb-207,Pb-208(d, p), Pb-208(d, d'), and Pb-208(p, p') reactions obtained with the Q3D magnetic spectrograph of the Maier-Leibnitz-Laboratorium at Garching (Germany) at scattering angles 15 degrees <= Theta <= 138 degrees and bombarding energies E-d = 22,24 MeV and 14.8 < E-p < 18.2 MeV, the excitation energy is determined as E-x = 5666.7 +/- 0.3 keV; the mean cross section in the nonresonant Pb-208(p, p') and the Pb-208(d, d') reactions is about 1 mu b/sr. A new state at E-x = 5042 +/- 3 keV is suggested to have the spin of 2(+). The 0(+) neutron pairing vibration state at E-x = 4868 keV and the 0(+) member of the double-octupole multiplet at E-x = 5241 keV are verified by the nonresonant Pb-208(p, p') and Pb-208(d, d') reactions with cross sections of around 3 mu b/sr.