Composition of the nuclear periphery from antiproton absorption using short-lived residual nuclei - art. no. 054309

The neutron-to-proton density ratio at the nuclear periphery was determined for six targets from the yield of nuclei with mass (A(t)-1) generated by a ntiproton annihilation on targets with mass number A(t). A new setup allowe d us to measure this yield for nuclei with half-lives down to 6 s. The expe riment confirmed the negative correlation between the peripheral neutron-to -proton density ratio and the neutron binding energy, which had been previo usly found. Results of Hartree-Fock Bogoliubov and relativistic Hartree-Bog oliubov calculations show good agreement for a large number of nuclei. By c omparing the measured values with those derived from Hartree-Fock-Bogoliubo v calculations, the ratio R of the imaginary parts of the effective scatter ing lengths of antiprotons on bound neutrons and protons was deduced to be R = 0.69(4). For the first time yields of several excited states of some (A (t)-1) nuclei have been investigated. [S0556-2813(99)04410-6].