New liquid drop model with the isospin-square dependence of the volume and surface energy terms is applied to reproduce experimentally known masses of nuclei with number of protons and neutrons larger or equal to twenty. The ground-state microscopic energy corrections are taken into account. In spite of the fact that the model contains only six adjustable parameters, the quality of mass reproduction is good, and it is comparable with other contemporary mass models. Also, the fission barrier heights of actinide nuclei evaluated using the topographical theorem of Myers and Swiatecki are close to the data.

Calculations to reconstruct rotational level patterns in the 220Rn and 226Ra nuclei have been performed using a collective quadrupole+octupole approach with microscopic mass tensor and moments of inertia dependent on deformation and pairing degrees of freedom. The main objective is to quantitatively confirm the known experimental observations that the Rn nucleus passes from octupole vibrational to octupole deformed with increasing rotation frequency, while the Ra nucleus is relatively weakly affected by collective rotation, being octupole deformed from the beginning. The collective potential in a nine-dimensional collective space is determined using the macroscopic-microscopic method with Strutinsky and the BCS with an approximate particle number projection microscopic corrections. The corresponding Hamiltonian is diagonalized based on the projected solutions of the harmonic oscillators coupled with Wigner functions. Such an orthogonalized basis is additionally symmetrized with respect to the so-called intrinsic symmetrization group, specifically dedicated to the collective space used, to ensure the uniqueness of the Hamiltonian eigensolutions in the laboratory frame. The response of the pairing and deformation degrees of freedom to external rotation is discussed in the variational approach, where the total energy is minimized by the deformation and pairing variables. As the nuclear spin increases, the pairing gaps of protons and neutrons decrease from its ground-state equilibrium values to zero (no superfluid solution). Consequently, the corresponding microscopic moments of inertia increase with collective spin (Coriolis antiparing effect), resulting in effectively lower rotational energy levels I pi with respect to pure classical-rotor pattern I(I + 1). The expression for cranking microscopic moments of inertia allows to discuss the rotational Hamiltonian term as depending on the nuclear structure. The effect of vibrations of the pairing field is considered only on average by introducing a multiplicative constant factor to rescale the moment of inertia values. The obtained comparison of experimental and theoretical rotational energy level schemes, dipole, quadrupole, and octupole transition probabilities of B(E)D) in 220Rn and 226Ra is satisfactory.

This study explores the phenomenon of shape coexistence in nuclei around ^172 Hg, with a focus on the isotopes ^170 Pt, ^172 Hg, and ^174 Pb, as well as the ^170 Pt to ^180 Pt isotopic chain. Utilizing a macro-microscopic approach that incorporates the Lublin–Strasbourg Drop model combined with a Yukawa-Folded potential and pairing corrections, we analyze the potential energy surfaces (PESs) to understand the impact of pairing interaction. For 170Pt, the PES exhibited a prolate ground state, with additional triaxial and oblate-shaped isomers. In ^172 Hg, the ground-state deformation transitions from triaxial to oblate with increasing pairing interaction, demonstrating its nearly γ -unstable nature. Three shape isomers (prolate, triaxial, and oblate) were observed, with increased pairing strength leading to the disappearance of the triaxial isomer. ^174 Pb exhibited a prolate ground state that became increasingly spherical with stronger pairing. While shape isomers were present at lower pairing strengths, robust shape coexistence was not observed. For realistic pairing interaction, the ground-state shapes transitioned from prolate in ^170 Pt to a coexistence of γ -unstable and oblate shapes in ^172 Hg, ultimately approaching spherical symmetry in ^174 Pb. A comparison between Exact and Bardeen–Cooper–Schrieffer (BCS) pairing demonstrated that BCS pairing tends to smooth out shape coexistence and reduce the depth of the shape isomer, leading to less pronounced deformation features. The PESs for even–even ^170-180 Pt isotopes revealed significant shape evolution. ^170 Pt showed a prolate ground state, whereas ^172 Pt exhibited both triaxial and prolate shape coexistence. In ^174 Pt, the ground state was triaxial, coexisted with a prolate minimum. For ^176 Pt, a γ -unstable ground state coexists with a prolate minimum. By ^178 Pt and ^180 Pt, a dominant prolate minimum emerged. These results highlight the role of shape coexistence and γ -instability in the evolution of nuclear structure, especially in the mid-shell region. These findings highlight the importance of pairing interactions in nuclear deformation and shape coexistence, providing insights into the structural evolution of mid-shell nuclei.

A new liquid drop model with iso-scalar volume and surface energy terms is applied to reproduce experimentally known masses of nuclei with a number of protons and neutrons larger or equal to twenty. The ground-state microscopic energy corrections are considered. Although the model contains only six adjustable parameters in its macroscopic part, the quality of mass reproduction is high and comparable with other contemporary mass estimates. Additionally, the fission barrier heights of actinide nuclei evaluated using the topographical theorem of Myers and Świa̧tecki are close to the data.

The neutron richness of the light charged particles emitted out of the fission plane in heavy ion reactions has been experimentally investigated via the production of A=3 mirror nuclei in ^86 Kr + ^nat Pb reactions at 25 MeV/u. The energy spectra and angular distributions of triton (t) and ^3 He in coincidence with two fission fragments are measured with the Compact Spectrometer for Heavy IoN Experiment (CSHINE). The energy spectrum of ^3 He is observed harder than that of triton in the fission events, in accordance with the phenomena reported as “ ^3 He-puzzle” in inclusive measurements. With a data-driven energy spectrum peak cut scenario, it is observed that the yield ratio R(t/^3He) increases with the angle to the fission plane, showing an enhancement of neutron-rich particle emission from out-of-fission-plane. A qualitative comparison with the transport model calculations suggests that this observation may serve as a new probe for the nuclear symmetry energy.

We present an in-depth investigation of heavy-ion fusion dynamics using a six-dimensional Langevin framework that enables unrestricted motion of the asymmetry parameter. The stochastic formalism naturally incorporates friction effects and energy fluctuations, providing a detailed understanding of the fusion process. The dynamics transition into the overdamped regime, facilitating rapid neck stabilization while effectively capturing the interplay between shape and rotational degrees of freedom. This approach achieves excellent agreement with experimental spin distributions and fusion cross-sections, establishing a robust foundation for forthcoming studies on the synthesis of superheavy elements and the exploration of the enigmatic fusion hindrance mechanism.

Spontaneous fission of 252Cf and fusion-induced fission of 250Cf are investigated within a multidimensional Langevin model. The potential-energy surface is calculated in the macroscopic-microscopic Lublin-Strasbourg drop (LSD) + Yukawa-folded approach using the four-dimensional (4D) Fourier-overspheroid shape parametrization. The dynamical evolution described by the Langevin equation is coupled to neutron evaporation, thereby allowing for the possibility of multichance fission. Charge equilibration and excitation-energy sharing between the fragments emerging at scission are evaluated, and their deexcitation is finally computed. The correlation between various observables, particularly the isotopic properties of the fragments, is discussed and compared with the experiment whenever available. The theoretical predictions are generally in good agreement with the data.

New liquid drop model with the isospin-square dependence of the volume and surface energy terms is applied to reproduce experimentally known masses of nuclei with number of protons and neutrons larger or equal to twenty. The ground-state microscopic energy corrections are taken into account. In spite of the fact that the model contains only six adjustable parameters, the quality of mass reproduction is good, and it is comparable with other contemporary mass models. Also, the fission barrier heights of actinide nuclei evaluated using the topographical theorem of Myers and Swiatecki are close to the data.

The role of pairing interactions on the scission configurations, the total kinetic energy, and the mass distribu-tions in U isotopes is investigated using the deformed mean-field plus standard pairing model. The total kinetic energy and the mass distributions of 232-238U isotopes obtained using the shape-dependent probability distribution expressed by the Wigner function reproduces the experimental data remarkably well. The model calculations show that the scission region is sensitive to the variation of the pairing interaction strength, particularly for the asymmetric and symmetric scission points. The apparent changes in the peak-to-valley ratio in mass distribution by varying the pairing interaction strength confirm that the pairing interaction plays an important role in achieving the scission process for 236U under the present model. These results also suggest that the pairing interaction strength in the current work should increase with the elongation of the nucleus to yield better fission products. Through numerical analysis, we provide possible microscopic pictures of spontaneous fission around the scission configurations in the exactly solvable pairing model.

We propose a new, rapidly convergent, the so-called Fourier over Spheroid (FoS), shape parametrization to model fission of heavy nuclei. Four collective coordinates are used to characterize the shape of the fissioning system, being its elongation, left-right asymmetry, neck size, and non-axiality. The potential energy landscape is computed within the macroscopic-microscopic approach, on the top of which the multi-dimensional Langevin equation is solved to describe the dynamics. Charge equilibration at scission and de-excitation of the primary fragments after scission are further considered. The model gives access to a wide variety of observables, including fission fragments mass, charge, and kinetic energy yields, fragment mean N/Z and post-scission neutron multiplicities, and importantly, their correlations. The latter are crucial to unravel the complexity of the fission process. The parameters of the model were tuned to reproduce experimental observation from thermal neutron-induced fission of 235U, and next used to discuss the transition from the asymmetric to symmetric fission along the Fm isotopic chain.

A new, rapidly convergent Fourier over spheroid parametrization is developed to describe the shape of a fissioning nucleus: its elongation, non-axiality and left-right asymmetry and neck formation. The 4D Potential Energy Surfaces (PES) of even-even actinide nuclei are evaluated within the macro-micro model. The Langevin trajectories generated on such PESs allow for obtaining the fission fragments' mass and kinetic energy yields. The charge equilibration at the scission configuration and the post-scission neutron emission are also discussed.

A rapidly converging 4-dimensional Fourier shape parametrization is used to model the fission process of heavy nuclei. Potential energy landscapes are computed within the macroscopic-microscopic approach, on top of which the multi-dimensional Langevin equation is solved to describe the fission dynamics. Charge equilibration at scission and de-excitation by neutron evaporation of the primary fragments after scission is investigated. The model describes various observables, including fission-fragment mass, charge, and kinetic energy yields, as well as post-scission neutron multiplicities and, most importantly, their correlations, which are crucial to unravel the complexity of the fission process. The parameters of the dynamical model were tuned to reproduce experimental data obtained from thermal neutron-induced fission of $^{235}$U, which allows us to discuss the transition from asymmetric to symmetric fission along the Fm isotopic chain.

The neutron rich neck zone created in heavy ion reaction is experimentally probed by the production of the $A=3$ isobars. The energy spectra and angular distributions of triton and $^3$He are measured with the CSHINE detector in $^{86}$Kr +$^{208}$Pb reactions at 25 MeV/u. While the energy spectrum of $^{3}$He is harder than that of triton, known as "$^{3}$He-puzzle", the yield ratio $R({\rm t/^3He})$ presents a robust rising trend with the polar angle in laboratory. Using the fission fragments to reconstruct the fission plane, the enhancement of out-plane $R({\rm t/^3He})$ is confirmed in comparison to the in-plane ratios. Transport model simulations reproduce qualitatively the experimental trends, but the quantitative agreement is not achieved. The results demonstrate that a neutron rich neck zone is formed in the reactions. Further studies are called for to understand the clustering and the isospin dynamics related to neck formation.

Two-body correlations of the isotope-resolved light and heavy clusters are measured in $^{86}$Kr+$^{\rm 208}$Pb reactions at 25 MeV/u. The yield and kinetic variables of the $A=3$ isobars, triton and $^3$He, are analyzed in coincidence with the heavy clusters of $7\le A \le 14$ emitted at the earlier chance. While the velocity spectra of both triton and $^3$He exhibit scaling behavior over the type of the heavy clusters, the yield ratios of ${\rm t/^3He}$ correlate reversely to the neutron-to-proton ratio $N/Z$ of the latter, showing the ping-pong modality of the $N/Z$ of emitted clusters. The commonality that the $N/Z$ of the residues keeps the initial system value is extended to the cluster emission in heavy ion reactions. The comparison of transport model calculations to the data is discussed.

We report the reconstruction method of the fast fission events in 25 MeV/u $^{86}$Kr +$^{208}$Pb reactions at the Compact Spectrometer for Heavy IoN Experiment (CSHINE). The fission fragments are measured by three large-area parallel plate avalanche counters, which can deliver the position and the arrival timing information of the fragments. The start timing information is given by the radio frequency of the cyclotron. Using the velocities of the two fission fragments, the fission events are reconstructed. The broadening of both the velocity distribution and the azimuthal difference of the fission fragments decrease with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also reveals consistently the dynamic feature the fission events.

We report a reconstruction method for fast-fission events in 25 MeV/u 86 Kr + 208 Pb reactions at the Compact Spectrometer for Heavy Ion Experiment(CSHINE). The fission fragments(FFs) are measured using three large-area parallel-plate avalanche counters, which can deliver the position and arrival timing information of the fragments. The start timing information is provided by the radio frequency of the cyclotron. Fission events were reconstructed using the velocities of the two FFs. The broadening of both the velocity distribution and azimuthal difference of the FFs decreases with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also consistently reveals the dynamic features of fission events.

Potential energy surfaces of even-even superheavy nuclei are evaluated within the macroscopic-microscopic approximation. A very rapidly converging analytical Fourier-type shape parametrization is used to describe nuclear shapes throughout the periodic table, including those of fissioning nuclei. The Lublin Strasbourg Drop and another effective liquid-drop type mass formula are used to determine the macroscopic part of nuclear energy. The Yukawa-folded single-particle potential, the Strutinsky shell-correction method, and the BCS approximation for including pairing correlations are used to obtain microscopic energy corrections. The evaluated nuclear binding energies, fission-barrier heights, and Q-alpha energies show a relatively good agreement with the experimental data. A simple one-dimensional WKB model a la Swiatecki is used to estimate spontaneous fission lifetimes, while alpha-decay probabilities are obtained within a Gamow-type model.

The Langevin approach is extendedly applied to study the dynamical process of nuclear fission within the Fourier shape parametrization, where the potential energy is calculated with the macroscopic-microscopic model based on the Lublin-Strasbourg drop model and the Yukawa-folded potential. The fragment mass distribution and the total kinetic energy as a function of heavy fragment mass in 14 MeV n + U-235 fission are calculated and compared with the evaluated data from ENDF/B-VIII.0 and the experimental data. It is found that the Wall model for the friction tensor is available to describe both of the mass distribution and the total kinetic energy (TKE) distribution in the nuclear fission within the present model. In addition, the mass distributions and the TKE distributions in 14 MeV n + U-233,U-236,U-238 and Pu-239 fission are well described. Furthermore, the behavior of the correlation of the distance between the centers of mass of two fragments with the heavy fragment mass at the scission point is found to be consistent with that of the TKE distribution where the shortest R-12 locates around A(h) = 135 which is due to the influence of the shell effects.

我们研究了在CSHINE上重建$ 25 MeV/u ^{86}Kr +^{208}Pb$ 反应中快裂变事件的方法。裂变碎片由三个大面积平行板雪崩计数器进行探测，它可以提供碎片的位置和到达的时间信息。起始时间信息由回旋加速器的高频信号给出。我们利用两个裂变碎片的速度，重建了裂变事件。裂变碎片的速度分布和方位差的展宽均随折叠角的增大而减小，这与快速裂变发生的图像一致。同时，裂变轴的各向异性角分布也一致地揭示了裂变事件的动力学特征。

Fission properties of the actinide nuclei are deduced from theoretical analysis. We investigate potential energy surfaces and fission barriers and predict the fission fragment mass yields of actinide isotopes. The results are compared with experimental data where available. The calculations were performed in the macroscopic-microscopic approximation with the Lublin-Strasbourg Drop (LSD) for the macroscopic part, and the microscopic energy corrections were evaluated in the Yukawa-folded potential. The Fourier nuclear shape parametrization is used to describe the nuclear shape, including the non-axial degree of freedom. The fission fragment mass yields of the nuclei considered are evaluated within a 3D collective model using the Born-Oppenheimer approximation.