Cross sections were measured for proton decay from isobaric analog states (IAS; $T=T_z+1\mathrm{}$) formed in the ($d,n$) reactions on the following targets: ${\mathrm{O}}^{16}$, ${\mathrm{Al}}^{27}$, ${\mathrm{Ni}}^{64}$, ${\mathrm{Zn}}^{68}$, ${\mathrm{Y}}^{89}$, ${\mathrm{Zr}}^{90,91,92,94}$, ${\mathrm{M}}^{92,94,98}$, ${\mathrm{Sn}}^{114,116,118,120}$, and ${\mathrm{Pb}}^{206}$. A $\Delta E-E$ detector telescope having a combined energy resolution of about 34 keV was used. Excitation functions (${\theta }_{\mathrm{lab}}={170}^{\circ }$) were obtained with the deuteron energies ranging from the ($d,n$) threshold of the IAS to about 16 MeV. Angular distributions were also obtained at the various incident energies for a few of the strong transitions. The cross sections are large only for reactions leading back to the target ground state when, in addition, the neutron decay channels are closed to the IAS. Particular attention is paid to the large variations in the cross sections for reactions proceeding through the analogs of $2d_{\frac{5}{2}}$, $3s_{\frac{1}{2}}$, and $2d_{\frac{3}{2}}$ states in Zr, Mo, and Sn isotopes. At incident energies several hundred keV above the ($d,n$) threshold, these variations are shown to be consistent with a sequential process in which the ($d,n$) formation mechanism is direct, when the decay through the spreading width is explicitly taken into account in the branching ratios. However, the over-all energy dependence of the ($d,n$) cross sections, particularly near threshold, deviate sharply from that predicted by a simple direct process in the stripping model. From the study of the angular distributions of the decay to the $0^{+}$ ground state from the $d_{\frac{5}{2}}(\mathrm{g}.\mathrm{s}.\mathrm{})$ IAS in ${\mathrm{Nb}}^{91*}$ and ${\mathrm{Tc}}^{93*}$, the $m$-substate populations of the IAS are extracted. The values at energies near threshold suggest the importance of spinorbit interactions in the ($d,n$) formation mechanism.

• Received 10 April 1968

DOI:https://doi.org/10.1103/PhysRev.173.1108