Intermediate-Mass Fragment Decay of the Neck Zone Formed in Peripheral ${}^{209}{Bi+}^{136}\mathrm{Xe}$ Collisions at ${\mathit{E}}_{\mathrm{lab}}/\mathit{A}=28\mathrm{}\mathrm{MeV}$

Intermediate-mass fragments (IMF) from the ${}^{209}{\mathrm{B}\mathrm{i}+}^{136}\mathrm{Xe}$ reaction at $E_{\mathrm{lab}}/A=28\mathrm{}\mathrm{MeV}$ have been measured in coincidence with other reaction products, using a highly efficient $4\pi$ detector setup. Their emission patterns exhibit features consistent with dynamical fragmentation of a neck zone between the reaction partners, in addition to sequential statistical emission. In peripheral collisions with an average of 0.3 GeV of dissipated kinetic energy, the dynamical process accounts for 0.24 of the observed IMF multiplicity of 0.33.