Compound Nucleus Effects in Deuteron Reactions: B10(d, p)B11 and B10(d, α)Be8

Abstract

Angular distributions and excitation curves have been measured in the energy range $E_d=0.9\mathrm{} \mathrm{to} 3.0$ Mev for the four highest energy proton groups from the ${\mathrm{B}}^{10}(d, p){\mathrm{B}}^{11}$ reaction and for the ground state $\alpha$-particle group from the ${\mathrm{B}}^{10}(d, \alpha ){\mathrm{Be}}^8$ reaction. Several broad resonances were observed in the excitation curves, but the shapes of the curves obtained for the various particle groups differ considerably. Resonance effects are most pronounced for the ground state proton group, whereas the group leading to the third excited state of ${\mathrm{B}}^{11}$ shows no resonance behavior. The ($d, p$) angular distributions suggest that compound nucleus formation plays an important role at these low bombarding energies. In particular, the stripping peak in the angular distribution of the ground state proton group ($p_0$) does not begin to take shape until $E_d\gtrsim 2$ Mev, while the $p_1$ distributions do not indicate a stripping peak at any energy. It is suggested that a shell-model effect is responsible for the lack of stripping in the case of the $p_1$ group. At $E_d=2.0\mathrm{}$ Mev, the $p_2$ angular distribution is almost symmetric about $\theta \left(\mathrm{cm}\right)=90\mathrm{}°$ while the $p_3$ distribution shows a fairly well developed $l_n=1\mathrm{}$ stripping peak. The $\alpha$-particle excitation curves indicate that forward-backward asymmetries in the the angular distributions are averaged out when the energy interval $E_d=1\mathrm{} \mathrm{to} 2.5$ Mev is considered, in accordance with the statistical model prediction.