A resonance in the ${\mathrm{Li}}^7$+$d$ reaction at a deuteron bombarding energy of 361±2 keV, corresponding to a level in ${\mathrm{Be}}^9$ at 16.97 MeV, has been investigated. Total cross sections for ${\mathrm{Li}}^7(d, p_0){\mathrm{Li}}^8$ were measured by detecting induced ${\mathrm{Li}}^8$ activity for deuteron energies between 340 and 780 keV. In agreement with earlier work of Woods and Wilkinson, a resonance in this reaction was observed on a background rapidly decreasing with decreasing deuteron energy. This resonance and the surrounding region from 0.1 to 1.1 MeV were also studied with the ${\mathrm{Li}}^7(d, \gamma ){\mathrm{Be}}^9$ reaction by measuring the yield of the gamma-ray transitions to the lower states of ${\mathrm{Be}}^9$ with a NaI crystal. The measured width of the level was less than 600 eV in the laboratory system. The angular distribution of the on-resonance gamma rays to the ground state was isotropic to within 7%. Branching ratios for the gamma rays to several states in ${\mathrm{Be}}^9$ were measured with a NaI crystal, a scintillation pair spectrometer, and a NaI crystal surrounded by an anticoincidence shield. The relative intensities for the gamma-ray transitions to the ground state and to the states at 1.70, 2.43, 3.04, and 4.74 MeV were found to be 100, 8.5±4.3, 10.6±5.3, ≤4.5, and 9.6±4.8, respectively. The 15.3-MeV gamma-ray transition indicates the existence of a level in the usual sense at 1.70 MeV in ${\mathrm{Be}}^9$. From the gamma-ray measurements below resonance at 300 keV an upper limit of 1.6×${10}^{-30\mathrm{}}$ ${\mathrm{cm}}^2$ was found for the direct ($d, \gamma$) cross section to low-energy states in ${\mathrm{Be}}^9$. For the ${\mathrm{Li}}^7(d, n)$ reaction, the yield of neutrons with energies above 10 MeV showed a resonance at the same energy. From neutron time-of-flight measurements relative to coincident gamma rays, neutron groups were seen corresponding to breakup of levels in ${\mathrm{Be}}^9$ at 2.43 and 4.74 MeV. The ${\mathrm{Li}}^7(d, d){\mathrm{Li}}^7$ and ${\mathrm{Li}}^7(\mathrm{d}, \alpha ){\mathrm{He}}^5$ reactions did not show observable resonance effects. From the above results, the reduced widths for neutron and alpha-particle emission are found to be considerably smaller than the corresponding width for protons, thus supporting the hypothesis that the state in ${\mathrm{Be}}^9$ at 16.97 MeV has an isobaric spin of $\frac{3}{2}$.

• Received 5 April 1965

DOI:https://doi.org/10.1103/PhysRev.139.B904