Fission mode identification in the Hg region; Derivative analysis approach

Kattikat Melcom, D. T.*; Tsekhanovich, I.*; Guezet, F.*; Andreyev, A. N.*; 西尾 勝久   

Kattikat Melcom, D. T.*; Tsekhanovich, I.*; Guezet, F.*; Andreyev, A. N.*; Nishio, Katsuhisa

Existence of several fission modes (paths) comes from the nuclear structure of fissiong system, and it has been discussed from the measurement of fission-fragment mass (FFMD) and total kinetic energy (TKE) distributions. For some cases, especially fission from highly excited states, the obtained FFMDs are in general structureless, which makes the identification of fission modes ambiguous and analysis dependent. It has been thus desired to develop a robust analysis approach aiming at identification of a number of major fission modes in FFMDs. For this purpose, we propose a method to calculate the second derivative of FFMD. Number of detected minima on the second derivative curve is relevant to the number of fission modes and thus determines the structure of the fit function to be used for the FFMD and TKE data description. This approach was adopted to the high-energy fission of Hg, populated by the Ar+Sm fusion reaction at the JAEA tandem facility. Compared to the previous analysis assuming only single asymmetric fission mode, the current approach shows also the signature of symmetric fission mode.