Quasifission Dynamics: Deformation and Orientation

Fusion reactions that lead to the formation of super-heavy compound nuclei are inhibited by competing processes such as quasifission, where the dinuclear system does not fully equilibrate and fuse to form a compound nucleus. For deformed nuclei, the orientation of colliding nuclei influences the probability of forming a compound nucleus. Axial/tip collisions have an empirical capture barrier [1][2][3] slightly below the average barrier due to decreased Coulomb repulsion from the formation of an elongated dinuclear system, but the elongated dinuclear system is less likely to equilibrate and form a compound nucleus, leading to increased quasifission outcomes. Equatorial/side collisions result in more compact shapes that are more likely to survive quasifission and form compound nuclei but have above average barriers due to increased Coulomb repulsion resulting from the more compact shape [1][2]. To further investigate the influence of orientation on quasifission and fusion-fission outcomes, we studied the reactions ^32,36S + ²³²Th at a range of energies from 93% to 99% of the average barrier [4]. The total capture cross section will be extracted from measured fission cross sections [5] [6]. The ongoing analysis of ³²S + ²³²Th will be discussed.

[1] K. Hammerton, et al., Physical Review C 99, 054621 (2019)

[2] D. J. Hinde, et al., PRL 74, 1295 (1995)

[3] D. Y. Jeung, et al., Physical Review C 103, 034603 (2021)

[4] D. J. Hinde, et al., PRL 101, 092701 (2008)

[5] R. du Rietz, et al., PRL 106, 052701 (2011)

[6] D. Y. Jeung. Ph.D. Thesis, The Australian National University (2018)