Speaker
Description
The interplay between macroscopic liquid-drop properties and microscopic effects represents a fundamental challenge in nuclear fission [1]. This competition can be probed through excitation-energy distributions, as experimental evidence shows a systematic attenuation of structure-dependent effects, thereby progressively revealing the underlying macroscopic component of the potential-energy surface. In this context, fission-fragment isotopic yields provide a sensitive observable for quantifying this evolution [2,3]. In the actinide region, fission at low energy is characteristically dominated by asymmetric mass splits driven by shell effects; however, increasing excitation energy reduces these structure-induced asymmetries and enhances the relative contribution of symmetric fission modes [4].
This specific approach is part of a systematic research campaign at GANIL designed to exploit transfer- and fusion-induced fission reactions in inverse kinematics [5-7]. A $^{238}$U beam at 5.88 AMeV impinged on four different targets ($^{27}$Al, $^{24}$Mg, $^{nat}$B and $^{9}$Be), populating a variety of actinides at low-to-moderate excitation energies. The use of inverse kinematics allows for the full isotopic identification (A, Z) and kinematic reconstruction of one of the fission fragments using the VAMOS++ spectrometer [8] in combination with the AGATA gamma-ray array [9]. Additionally, the use of SPIDER silicon telescope to detect the target-like recoil produced in the transfer reaction, enables an event-by-event characterisation of the fissioning system [6].
In this framework, the present study focuses on the evolution of fission-fragment isotopic yield distributions for selected actinides as a function of excitation energy. Furthermore, the impact of the incoming channel in the fission dynamics is investigated by comparing the fission-fragment production from different reactions leading to the same fissioning system.
References
[1] V. Strutinsky, Nuclear Physics A 95, 420–442 (1967).
[2] K.-H. Schmidt et al., Reports on Progress in Physics 81, 106301 (2018).
[3] A. N. Andreyev et al., Reports on Progress in Physics 81, 016301 (2017).
[4] K. Nishio et al., Phys. Rev. C 111, 044609 (2025).
[5] M. Caamaño et al., Phys. Rev. C 88, 024605 (2013).
[6] C. Rodríguez-Tajes et al., Phys. Rev. C 89, 024614 (2014).
[7] D. Ramos et al., Phys. Rev. C 97, 054612 (2018).
[8] M. Rejmund et al., Nuclear Instruments and Methods in Physics Research Section A 646, 184–191 (2011).
[9] E. Clément et al., Nuclear Instruments and Methods in Physics Research Section A 855, 1–12 (2017).