The isospin-nonconserving ($d,\alpha$) reactions on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ leading to the $0^{+}$, $T=1\mathrm{}$ states at $E_x=2.31\mathrm{}$ MeV in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ and $E_x=1.74\mathrm{}$ MeV in ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$ have been studied in the energy intervals of $E_d=14.0\mathrm{} \mathrm{to} 18.1$ MeV and 26.2 to 29.5 MeV, respectively. Two resonances were observed in the excitation function for the reaction on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at $E_d=14.4\mathrm{} \mathrm{and} 15.0$ MeV followed by a weak tail with little energy dependence. This behavior is similar to that observed earlier for the reaction on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in the same energy region. The results for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at the higher bombarding energies, in conjunction with arguments related to the properties of highly excited states, appear to favor a direct- or semidirect-reaction mechanism. Consistent with the observed facts are virtual $E1\mathrm{}$ Coulomb excitation of the deuteron or the preferential spin-flip process suggested by Noble. No evidence was found for the two-step process involving isospin-mixed intermediate states, which was also suggested by Noble.

• Received 1 October 1970

DOI:https://doi.org/10.1103/PhysRevC.3.79