Gamma-ray angular correlations have been measured for the damped reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{28}$Si${,}^{12}$C${)}^{28}$Si between ${\mathrm{\theta }}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=120° and 160° for ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=43.5 and 48 MeV. The spin alignments and density matrices have been deduced from the observed angular distribution of the gamma rays for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ states in -10<Q<0 and -16<Q<0 MeV for ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=43.5 and 48 MeV, respectively, and for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($2_1^{+}$) state in strongly damped region Q<-10 MeV. We find that the spin angular momenta of the nuclei are poorly aligned with respect to the normal to the reaction plane and the density matrices for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($2_1^{+}$) and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ states are almost diagonal with respect to the direction of motion of the outgoing particle. We also find qualitatively similar behavior of the spin alignments for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ states in strongly damped region. The measured density matrices and spin alignments are consistent with the picture of formation of a long-lived dinuclear complex undergoing orbiting, bending, and wriggling motions, but not with those obtained from statistical compound nucleus or sticking-model calculations.

• Received 19 July 1990

DOI:https://doi.org/10.1103/PhysRevC.43.1789