Speaker
Dr
Edward Simpson
(Australian National University)
Description
Above barrier fusion of light, weakly-bound projectiles with heavy targets is known to be suppressed by 25-35% [1-3]. Direct breakup reactions were thought to significantly reduce the probability for fusion of the entire projectile. Transfer reactions populating unbound states in neighbouring nuclei, such as $^5$Li and $^8$Be, have also been found to be a significant trigger of projectile disintegration [4].
Understanding the detail of these processes is crucial [5]: breakup must occur prior to the reactants reaching their mutual barrier in order to suppress fusion. If narrow, long-lived resonances are populated (e.g., $^6$Li 3$^+$ τ≈3×10$^{-20}$ s, $^8$Be 0$^+$ τ≈10$^{-16}$ s), the projectile-like nucleus will remain intact until it reaches the barrier, so cannot suppress fusion. Short lived states (e.g., the $^8$Be 2$^+$) disintegrate more quickly, but with ~10$^{-21}$ s collision timescales their effect on fusion is not yet clear.
Here we discuss recent Australian National University measurements of sub-barrier breakup, where absorption of the charged breakup fragments is minimal. We interpret these results using a classical dynamical model [6] that has been extended to account for the energies and lifetimes of resonant states, and discuss what the angular correlations of the fragments may reveal about the location of breakup.
[1] M. Dasgupta et al., Phys. Rev. C 66, 041602(R) (2002).
[2] Y. W. Wu et al., Phys. Rev. C 68, 044605 (2003).
[3] M. Dasgupta et al., Phys. Rev. C 70, 024606 (2004).
[4] D. H. Luong et al., Phys. Lett. B 695, 105 (2011); Phys. Rev. C 88, 034609 (2013).
[5] E. C. Simpson et al., Phys. Rev. C 93, 024605 (2016)
[6] A. Diaz-Torres et al., Phys. Rev. Lett. 98, 152701 (2007).
Primary author
Dr
Edward Simpson
(Australian National University)
Co-authors
Dr
D. H. Luong
(Australian National University)
Prof.
David Hinde
(Australian National University)
Mr
I. P. Carter
(Australian National University)
Ms
K. J. Cook
(Australian National University)
Prof.
Mahananda Dasgupta
(Australian National University)
Dr
Sunil Kalkal
(Australian National University)
