Abstract
Cross sections have been measured for the reaction Pb(γ,p) leading to the low-lying (1/2, 3/2) and (11/2, 5/2) doublets and 7/2 state in Tl using a high energy-resolution tagged photon beam of 41 to 57 MeV. The data are compared with results obtained with the reaction Pb(e,e′p) in the same recoil-momentum range. The recoil-momentum distributions derived from the (γ,p) data do not coincide with those obtained from the (e,e′p) data. Distorted-wave impulse-approximation (DWIA) calculations of which the input is constrained by the (e,e′p) data underestimate the (γ,p) data by typically one order of magnitude. An estimate of meson-exchange currents (MEC) effects using the Siegert theorem brings the DWIA-calculations close to the data. Random-phase approximation calculations also give a fair account of the data, but in this case MEC-effects are predicted to be less important.
Original language | English |
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Pages (from-to) | 13-18 |
Number of pages | 6 |
Journal | Physics Letters B |
Volume | 356 |
Issue number | 1 |
Publication status | Published - 1 Jan 1995 |