Proton-induced reactions on Y89

The reactions Y89(p, t)Y87, Y89(p, d)Y88, and Y89(p, α)Sr86 are studied with 27.8-MeV protons and solid-state-detector telescopes. A recent revision of the mass of Y87 is confirmed. Angular distributions are obtained for the observed states. Several new levels are found in Y87. The states at 0.98, 1.85, and 2.09 MeV are assigned Jπ=32-, 12-, and 32-, respectively. In Y89, the existence of two low-spin states of opposite parity is established at 0.705 MeV. Distorted-wave Born-approximation (DWBA) calculations are carried out for the (p, d) and (p, t) data. Good fits to the data are obtained for the (p, d) reaction, but the l=4 and l=1 summed strengths deviate in opposite directions from the sum rules. Poor fits are obtained for L=0 transitions in the (p, t) reaction on Y89 and the experimental L=2 angular distributions show features that are not reproduced by the DWBA. Multistep contributions are suggested. The data for the (p, α) reaction show some evidence for direct-reaction processes, but DWBA calculations cannot be carried out. NUCLEAR REACTIONS Y89(p, d), (p, t), (p, α), E=27.8 MeV; measured σ(E, θ), θ=9-50°, Δθ=3-4°, resolution 35-60 keV; deduced Y87-Y88 mass difference, Y87,88, Sr86 levels; DWBA analysis, deduced S for Y88.