Kyle Brown

Timescale for equilibration of N/Z gradients in dinuclear systems

Equilibration of N/Z in binary breakup of an excited and transiently deformed projectile-like fragment (PLF*), produced in peripheral collisions of 64Zn + 27Al, 64Zn, 209Bi at E/A = 45 MeV, is examined. The composition of emitted light fragments (3<=Z<=6) changes with the decay angle of the PLF*. The most neutron-rich fragments observed are associated with a small rotation angle. A clear target dependence is observed with the largest initial N/Z correlated with the heavy, neutron-rich target. Using the rotation angle as a clock, we deduce that N/Z equilibration persists for times as long as 3-4 zs (1zs = 1 x 10^-21 s = 300 fm/c). The rate of N/Z equilibration is found to depend on the initial neutron gradient within the PLF*.

Tracking saddle-to-scission dynamics using N/Z in projectile breakup reactions

Fragments produced in binary splits of an excited projectile-like fragment (PLF*) formed in the reactions 124Xe + 112,124Sn at an incident energy of 50 MeV/A are examined. The dependence of the isotopic composition of light fragments (4≤ ZL ≤8) on rotation angle allows one to explore changes in N/Z on the timescale of the rotational period of the PLF*. Entrance channel effects are examined by comparing the isotopic composition of fragments produced in the binary decay following 64Zn + 27Al, 64Zn, 209Bi at an incident energy of 45 MeV/A.

Fusion of 20O incident ions with 12C target nuclei

Evaporation residues resulting from fusion of 20O incident ions with 12C target nuclei have been measured for the first time. The cross-section associated with compound nuclei that de-excite via emission of charged particle is extracted. The resulting excitation function is compared with the predictions of a standard fusion model followed by statistical decay code. A significant underprediction of the measured cross-section by the fusion-evaporation model raises the question of whether the fusion cross-section is larger for the neutron-rich projectile or the statistical de-excitation is incorrectly predicted. Improvements in the experimental technique which should allow future measurement of the total fusion cross-section are described.