Studies of states in 153Eu and 155Eu with the (t, p) reaction

The 151, 153Eu(t, p)153, 155Eu reactions have been studied using 15 MeV tritons from the Los Alamos tandem Van de Graaff accelerator. The reaction products were analyzed with a Q3D magnetic spectrometer and detected with a helical-cathode position-sensitive proportional counter. Spectra were recorded at ten angles with the 151Eu target and at five angles with the 153Eu target. Characteristic two-nucleon transfer L = 0 angular distributions permit Iπ = 52+ assignments for levels at 173, 694, 706, 1150, 1442 and 1475 keV in 153Eu and at 0, ≈ 980, 1067, 1230 and ≈ 1480 keV in 155Eu. The ground-state transition connecting the two “deformed” nuclei 153Eu and 155Eu contains ≈ 86 % of the L = 0 strength. In contrast, the L = 0 strength in the 151Eu(t, p)153Eu reaction is severely fragmented and ⪅ 1 % of it is in the ground-state transition. This is attributed to differences in the wave functions of the odd proton and in the deformations of the N = 88 and 90 ground states. At most ≈ 12 of the observed L = 0 strength goes to states at low excitation energies which may be deformed, and the rest goes to states at higher energies. This appears to be analogous to the 150Sm(t, p)152Sm reaction in which ≈ 60 % of the L = 0 cross section goes to excited 0+ states in 152Sm.