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Description
One of the key ingredients for the synthesis of Super Heavy Elements (SHE) is the target-projectile combination of the reaction. The role of deformed target on the various Compound and non-Compound reaction mechanisms is yet to be explored [1,2]. The synthesis of SHE is further hindered by the Quasifission mechanism that competes with the formation of a Compound nucleus. The investigation of mass-energy distributions of heavy nuclei allows a detailed understanding of the associated various reaction mechanisms, and therefore is highly desirable to study the Quasifission process [3]. Furthermore, the region of neutron-deficient $Th$ nuclei has not been extensively studied for the multimodal fission phenomenon, which further builds on the primary motivation of the present study [4].
The experiment was performed at the Flerov Laboratory of Nuclear Reactions (FLNR), JINR, Russia, using an energetic $^{48}$Ca beam delivered from the $U400$ cyclotron. A thin target of $^{176}$Yb with thickness of about 214 $\mu$g/cm$^{2}$ on 1.5 $\mu$m thick Titanium backing was bombarded with the $^{48}$Ca beam at six different energies in the range of E$_{beam}$ = 188 to 272 MeV. The measurement of the reaction binary products was carried out by utilizing the double-arm time-of-flight (TOF) spectrometer CORSET [5]. Assuming the conservation of mass of the composite system of projectile and target, the double-velocity method was employed to determine the mass and energy of the reaction products.
The present reaction, $^{48}$Ca $+$ $^{176}$Yb, leads to the formation of the composite system, $^{224}$Th above the Coulomb barrier. The Mass-Total Kinetic Energy (M-TKE) distributions of the primary binary fragments from $^{224}$Th have been obtained from the present measurement. The measured M-TKE distribution profiles have been deconvoluted with multiple Gaussian functions to extract the yield contributions of the symmetric and asymmetric components from the fission-like fragments. Due to a comparatively high Coulomb factor, Z$_{1}$Z$_{2}$ = 1400 and a mass asymmetry value of about 0.57, significant suppression of the compound nucleus, $^{224}$Th formation because of enhanced contribution from the Quasifission process is expected. The target nucleus, $^{176}$Yb being highly prolate deformed in the ground state ($\beta_{2}$ = 0.3) when bombarded with spherical projectile beam particles of doubly magic $^{48}$Ca will further allow to investigate the role of deformed target on the reaction mechanism.
References:
1. G. N. Knyazheva $\it{et}$ $\it{al.}$, Phys. Rev. C $\bf{75}$, 064602 (2007).
2. D. J. Hinde $\it{et}$ $\it{al.}$, Phys. Rev. C $\bf{53}$, 1290 (1996).
3. E. M. Kozulin $\it{et}$ $\it{al.}$, Phys. Rev. C $\bf{105}$, 024617 (2022).
4. M. G. Itkis $\it{et}$ $\it{al.}$, Nucl. Phys. A $\bf{654}$, 870c (1999).
5. E. M. Kozulin $\it{et}$ $\it{al.}$, Instrum. Exp. Tech. $\bf{51}$, 44 (2008).
