The stripping reaction (α${,}^3$He) at 183 MeV bombarding energy has been used to study the neutron-particle response function on ${}_{}{}^{124,122,120,118,116,112}{}_{}{}^{}\mathrm{Sn}$ target nuclei up to 25 MeV excitation energy. Strong transitions to high-lying neutron states are observed beyond 4 MeV excitation energy. These transitions, arising from neutron stripping to high-spin outer subshells, appear as a sharp and strong peak located around 5 MeV excitation energy for the heavier tin isotopes (125, 123, and 121) and a broader structure extending up to 10 MeV. A clear broadening of the whole structure and the disappearance of the sharp component is observed with decreasing mass number, leading to a structureless spectrum in the case of ${}_{}{}^{113}{}_{}{}^{}\mathrm{Sn}$. Our investigation reveals a strong excitation of the 1${\mathit{i}}_{13/2}$ neutron strength, with possible mixture with the neighboring 1${\mathit{h}}_{9/2}$ and 2f subshells between 5 and 10 MeV excitation energy. The empirical data are compared with the theoretical predictions from the quasiparticle-phonon nuclear model. The present investigation, on a wide range of the tin isotopic chain, allows us to establish a comparison between the damping of high-lying particle and deep-hole states in heavy nuclei.

• Received 18 July 1990

DOI:https://doi.org/10.1103/PhysRevC.43.1687