Insights into Quasifission Dynamics from Mass-Angle Distribution Measurements
D. J. Hinde 1*, R. du Rietz 1, M. Dasgupta 1
1 Australian National University, Canberra, Australia
The formation of very heavy elements is suppressed by fission of the composite system before a compact compound nucleus is formed. This is known as quasifission. The basic reason for quasifission is the large Coulomb energy of two massive nuclei in contact, which drives the system apart after some exchange of mass and charge. Although the occurrence of quasifission is associated with the Coulomb energy, the effects of nuclear structure also influence the outcomes.
Recent experimental measurements of mass-angle distributions (MAD) have isolated different ways in which nuclear structure plays a significant role in determining reaction outcomes.
Reproducing the timescale of the quasifission process is a key constraint on theoretical models. Reliable information on reaction times can be obtained from MAD, and these are compared with times extracted from neutron multiplicities, and from recent crystal blocking measurements for quasifission reactions, to investigate consistency.
Measured mass-angle distributions for reactions forming Z=102,104. Projected mass-ratio spectra are shown below. Gaussian fits to the region around mass-ratio 0.5 (turquoise curves) change significantly from reaction to reaction. The red curves represent the mass distributions expected for fusion-fission.