Direct proton decay of the isoscalar giant dipole resonance in Pb-208

The excitation and subsequent proton decay of the isoscalar giant dipole resonance (ISGDR) in Pb-208 have been investigated via the Pb-208(alpha,alpha'p)(TI)-T-207 reaction at 400 MeV. Excitation of the ISGDR has been identified by the difference-of-spectra method. The enhancement of the ISGDR strength at high excitation energies observed in the multipole-decomposition-analysis of the singles Pb-208(alpha,alpha') spectra is not present in the excitation energy spectrum obtained in coincidence measurement. The partial branching ratios for direct proton decay of ISGDR to low-lying states of (TI)-T-207 have been determined and the results are compared with predictions of continuum random-phase-approximation (CRPA) calculations. (C) 2009 Elsevier B.V. All rights reserved.