Fragmentation of Necklike Structures

Intermediate mass fragment (IMF: $3\le Z\le 20$ emission from necklike structures joining projectilelike and targetlike residues has been observed for peripheral ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ + ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Cu}$ collisions at $\frac{E}{A}=50\mathrm{}$ MeV. These fragments are emitted primarily at velocities between those of the projectilelike and targetlike residues. Relative to the charge distribution of fragments evaporated from projectilelike residues, the distribution for "neck" emission shows an enhanced emission for fragments with $4\le Z_{\mathrm{IMF}}\le 12$. This feature is consistent with expectations for the fragmentation of a noncompact cylindrical configuration.