학술논문
Fission of 215Fr studied with gamma spectroscopic methods
Document Type
Working Paper
Author
Miernik, K.; Korgul, A.; Poklepa, W.; Wilson, J. N.; Charles, G.; Czajkowski, S.; Czyż, P.; Fijałkowska, A.; Fraile, L. M.; Garczyński, P.; Hauschild, K.; Hiver, C.; Kurtukian-Nieto, T.; Lebois, M.; Llanos, M.; Lopez-Martens, A.; Treasa, K. M. Deby; Ljungvall, J.; Matea, I.; Mielczarek, J.; Murias, J. R.; Pasqualato, G.; Skruch, A.; Solak, K.; Stoyachev, K.; Tsekhanovich, I.
Source
Subject
Language
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.