Alpha-cluster pickup from Te and Sn isotopes with the (d, 6Li) reaction

Abstract

The reactions 122, 124, 126, 128, 130Te(d, 6Li) 118, 120, 122, 124, 126Sn and 112, 116, 118, 120, 122, 124, 126Sn(d, 6Li) 108, 112, 114, 116, 118, 120Cd have been investigated at E d = 33 MeV for states up to E x = 3 MeV or higher using magnetic analysis. Alpha-particle spectroscopic factors and reduced α-widths have been extracted with zero- and finite-range distorted wave Born approximation (DWBA) theory. Spectroscopic amplitudes were calculated from shell-model configurations including core excitations and a semi-microscopic analysis was performed for ground state transitions, proton pairing vibration states, as well as certain states with J π ≠ 0 +. Good agreement is obtained for the transitions to the Cd ground states provided DWBA is normalized to α-decay. The ground states and proton pairing vibration states in the heavy Sn isotopes appear to be strongly mixed. Increased collectivity, predicted by the interacting boson model, affects the excitation energies and transition strengths of the 0 + proton pairing vibration states in Sn in the middle of the neutron shell. Selectivity and coherence phenomena are also prevalent for states with J π ≠ 0 + and are interpreted microscopically. In particular, coherent contributions from proton pair and neutron pair excitations lead to enhancements not observed in two-nucleon transfer. The mass excess of 120Cd was measured as −83975 ± 25 keV. About 25 previously unknown states were observed in the Sn and Cd isotopes and about 30 spin-parity assignments were made.