Fission of 215Fr studied with gamma spectroscopic methods

Author:

K. Miernik, A. Korgul, W. Poklepa, J. N. Wilson, G. Charles, S. Czajkowski, P. Czyż, A. Fijałkowska, L. M. Fraile, P. Garczyński, K. Hauschild, C. Hiver, T. Kurtukian-Nieto, M. Lebois, M. Llanos, A. Lopez-Martens, K. M. Deby Treasa, J. Ljungvall, I. Matea, J. Mielczarek, J. R. Murias, G. Pasqualato, A. Skruch, K. Solak, K. Stoyachev, I. Tsekhanovich

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex)

journal:

date:

2023-11-23 00:00:00

Abstract

Background: Asymmetric fission is known to occur in two regions, the actinides and sub-lead, and is dependent on the fissioning system excitation energy. Experimental evidence in the sub-lead region show that this mode is surprisingly persistent with increasing energy and its origin is not fully understood. Purpose: To experimentally study the fusion-fission reaction of $^{215}$Fr at moderate excitation energy and determine previously unknown independent fission yields and other properties. Method: The compound nucleus was formed in the reaction $^{18}$O + $^{197}$Au. The prompt gamma-rays emitted during the reaction were measured with the high efficiency and high granularity $\nu$-ball2 spectrometer. Independent fission yields of even-even nuclei were determined by detecting triple-gamma cascades in the fission fragments. Results: The observed yields, although dominated by a symmetric peak, show maxima for heavy fragment of $Z \approx 54-56$, which is consistent with the known results in the actinide region but unexpected for the nuclide of interest, and at the studied excitation energy. Conclusions: The mode of asymmetric fission is present even at relatively high excitation energies in the system studied. This observation matches experimental findings in the sub-lead region, contrary to the actinides, and so far there is no well-developed explanation of this phenomenon.

PDF: Fission of 215Fr studied with gamma spectroscopic methods.pdf