A study has been made of the $\gamma$-ray deexcitation following deeply inelastic collisions between 100 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$. An experimental apparatus including a gas proportional particle telescope, a Ge(Li) detector, and three NaI(T1) detectors was used. All possible particle-$\gamma$ and particle-multiple-$\gamma$ coincidences for projectilelike fragments with $Z\ge 3$ were recorded. Yields and anisotropies of several discrete transitions were measured, as well as the mean and width of the gross multiplicity distribution as a function of detected $Z$ and reaction inelasticity. Estimates of average $\gamma$-ray transition energy, average energy carried by $\gamma$-ray deexcitation, and the degree of side feeding in observed $\gamma$ cascades were made. Observed anisotropies are consistent with considerable fragment spin alignment being present. Values of mean $\gamma$-ray multiplicity never exceed simple sticking model predictions; particle emission effects are seen to be important. The summed radiative strength of observed discrete line transitions is found to be less than unity, sometimes considerably so, for most deeply inelastic collisions. A short discussion is given of insights obtained on the entry state distribution for $\gamma$-ray emission and of the results of statistical model calculations of the relative yields of observed final states.

NUCLEAR REACTIONS ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$,$X\gamma )$, $E=100\mathrm{}$ MeV; measured $X-\gamma$ coinc, Ge(Li) detector; measured $X-\gamma -\gamma$ multiplicity, Ge(Li), NaI detectors; deduced decay product yields, alignment, radiative strengths, $\gamma$ multiplicity mean and width.

• Received 20 April 1981

DOI:https://doi.org/10.1103/PhysRevC.25.1304