Multinucleon Transfer Reactions Research Articles

Theoretical study of mass distribution in multinucleon transfer reactions

Theoretical study of mass distribution in multinucleon transfer reactions

Inverse transfer mechanisms in multinucleon transfer reactions

Inverse transfer mechanisms in multinucleon transfer reactions

Study of nucleus orientation effect in the 238U+238U multinucleon transfer reaction

The improved quantum molecular dynamics model was employed to study the 238U+238U multinucleon transfer reaction at E c.m. = 833 MeV in this work. The influence of the orientation effect on the nuclear deformation at the contact moment, the composite system lifetime, the transfer rate and the fragment production mechanism are investigated. Statistical analysis reveals that at the contact moment, the orientation of the projectile and the target have less influence on each other and retain their respective initial characteristics to some extent. For collision parameters less than 6 fm, significant differences are observed in composite system lifetime and transfer rate under different orientation configurations; however, the orientation effect gradually diminishes with increasing collision parameters. Additionally, it is found that transfer reactions dominate when the collision parameter b ≤ 6 fm, while elastic and inelastic scattering events increase rapidly as the collision parameter exceeds 6 fm. Within the range of 10 ≤ b ≤ 13 fm, the transfer probability for side–side collisions is significantly higher compared to other cases.

Ion-optical simulations for the NEXT solenoid separator

In this paper, we present ion-optical simulation for the design studies of a new solenoid separator as part of the NEXT experiment. Our aim is to separate Neutron-rich, EXotic, heavy nuclei produced in multinucleon Transfer reactions (NEXT) from the primary beam and un-wanted by-products within the magnetic field. The goal of the simulation is to find the optimum arrangement of the components within the NEXT solenoid separator to achieve the highest transmission efficiencies of transfer products and a good suppression of background. In our simulations, we focused on two complementary reactions to produce transfermium isotopes and to produce neutron-rich nuclei around the neutron number N = 126. Transmission yields above 50% for the transfermium isotopes of interest were reached in the simulations. The simulated yields for N = 126 lie between 5% and 20%.

Study of the Possibility of Obtaining Neutron-Enriched Isotopes with the Magic Number N = 126 in the Multinucleon Transfer Reactions Induced by Radioactive Ion Beams

Study of the Possibility of Obtaining Neutron-Enriched Isotopes with the Magic Number N = 126 in the Multinucleon Transfer Reactions Induced by Radioactive Ion Beams

Angular distribution of products in multinucleon transfer reactions* *Supported by the Guangdong Major Project of Basic and Applied Basic Research (2021B0301030006), the National Natural Science Foundation of China (12175151, 12105181, 11847235), and the Steady Support Program for Higher Education Institutions of Shenzhen (20200817005440001)

A method based on the dinuclear system (DNS) is proposed to describe the angular distribution of products in multinucleon transfer (MNT) reactions. By considering fluctuation effects, the angular distributions of reactions involving 136Xe+208Pb, 136Xe+209Bi, 86Kr+166Er, 84Kr+209Bi, and 84Kr+208Pb are examined, demonstrating good agreement with experimental data. Moreover, the double differential cross-sections ( and ) of reactions 136Xe+208Pb and 136Xe+209Bi are analyzed to explore the mechanism of angular distribution in MNT reactions. Additionally, the optimal angles for detecting N=126 isotopes are determined via an analysis on the influence of proton and neutron numbers of the projectiles on the angular distribution of the N=126 isotopic line. The results of this study can provide valuable insights for experimental detection.

In-cell multi-nucleon transfer reactions at the FRS Ion Catcher

An exploratory program to establish the multi-nucleon transfer (MNT) reaction as a new research direction at the FRS Ion Catcher (FRS-IC) has started at GSI. Its long term goal is the use of secondary exotic beams from the Super-FRS to drive MNT reactions. The near term goal is to perform proof-of-principle cross section and mass measurements with slowed-down 238U beams on targets inside the FRS-IC gas cell. The experimental efficiencies and expected rates are estimated using production cross sections from the Langevin MNT model followed by simulations of the full setup. The impact of the space charge effect inside the gas cell is evaluated in detail.

Shell effects on the drift and fluctuation in multinucleon transfer reactions

Shell effects on the drift and fluctuation in multinucleon transfer reactions

First investigation on the isomeric ratio in multinucleon transfer reactions: Entrance channel effects on the spin distribution

The multinucleon transfer (MNT) reaction approach was successfully employed for the first time to measure the isomeric ratios (IRs) of 211Po isomer (25/2+) and its ground state (9/2+) at the IGISOL facility using a 945 MeV 136Xe beam impinged on 209Bi and natPb targets. The dominant production of isomers compared to the corresponding ground states was consistently revealed in the α-decay spectra. Deduced IR of 211Po populated through the 136Xe+natPb reaction was found to have an enhancement of ≈1.8-times than that observed for the 136Xe+209Bi. State-of-the-art Langevin-type model calculations have been utilized to estimate the spin distribution of an MNT residue. The computations qualitatively corroborate with the considerable increase in the IRs of 211Po produced from 136Xe+natPb compared to 136Xe+209Bi. Theoretical investigations indicate a weak dependence of target spin on the IRs. The enhancement of the 211Po isomer in the 136Xe+natPb over 136Xe+209Bi can be attributed to the different proton (p)-transfer production routes. Estimations demonstrate an increment in the angular momentum transfer, favorable for isomer production, with increasing projectile energy. Comparative analysis reveals the two entrance channel parameters, projectile mass and p-transfer channels, strongly influencing the population of the high-spin isomer of 211Po (25/2+). This letter reports the first experimental and theoretical study on the IRs of nuclei formed from two different p-transfer channels via two independent MNT reactions.

Spectroscopy of neutron-rich nuclei produced by multinucleon transfer reactions at KISS

Properties such as lifetimes and masses of neutron-rich nuclei are key parameters for elucidating the astrophysical rapid neutron capture process (r-process). Due to the lack of experimental nuclear data in the relevant extremely neutron-rich region, especially near and above N = 126, the predictions of theoretical nuclear models are crucial for simulating r-process nucleosynthesis. Experimental studies of the properties and structures of neutron-rich nuclei from near the β stability line up to the r-process path provide important inputs to these theoretical models, improving the accuracy of predictions for the nuclear properties involved in the rprocess. We are developing the KEK Isotope Separation System (KISS) at the RIKEN RIBF facility to produce and separate these nuclei to perform spectroscopy experiments. The nuclei of interest are produced by multinucleon transfer reactions, which have been recently attracting renewed interest as they provide a way to access neutron-rich nuclei that are difficult to produce by other methods such as complete fusion or fragmentation. We have performed nuclear and laser spectroscopy, lifetime and mass measurements of neutron-rich nuclei of refractory elements near the N = 126 region using 198,natPt, natTa, natW, and natIr targets irradiated with 136Xe beams. We also extend our spectroscopic studies into the neutron-rich actinide region using 238U beams. This paper introduces the KISS facility and provides an overview of the nuclear spectroscopy experiments carried out there. We also introduce the KISS-1.5 project, which was started in FY2024 to further extend the research into the neutron-rich region.

Insights from multinucleon transfer reactions in 206Pb+118Sn

Multinucleon transfer reactions for the 206Pb +118 Sn system were measured at Elab = 1200 MeV using the PRISMA large solid-angle magnetic spectrometer. The experiment was conducted at laboratory angles around the grazing angle, covering an angular range of approximately 20°. The resulting differential and total cross sections, along with Q-value distributions for various neutron and proton pick-up and stripping channels, are presented. The Q-value distributions suggest a transition from quasi-elastic to deep inelastic collision processes, particularly in channels involving nucleon transfers. The experimental results have been compared with GRAZING code calculations, showing good agreement for few-nucleon transfer channels, while channels with large nucleon transfers are underestimated, indicating the involvement of more complex processes.

Population of heavy neutron-rich nuclei in multinucleon transfer reactions

Selected results recently obtained in studies of heavy ion transfer reactions at energies close to the Coulomb barrier are presented. In particular, the production of neutron-rich heavy nuclei via multinucleon transfer processes in 206Pb+118Sn, 197Au+130Te, and 94Rb+208Pb is discussed.

Study of transfer-like fragments for 136Xe+209Bi/176Yb: Prospect for multinucleon transfer reactions at IGISOL

Multinucleon transfer (MNT) reactions have been demonstrated as a promising pathway to produce and study very neutron-rich heavy nuclei, which can enhance our understanding of the nuclear structural features relevant to the r-process. Translead fragments were produced from the MNT reaction approach using 136Xe+209Bi at IGISOL utilizing an MNT gas cell. The 211Bi, 211mPo, 211Po, and 212mPo nuclei have been observed prominently in the α-decay spectrum. The Geant4 simulation, which played a crucial role in optimizing the experimental parameters, reveals broader angular-energy distributions of MNT fragments released from a thick target compared to those observed from the GRAZING and Langevin models for a mono-energetic beam. Comparative yield analyses of MNT fragments for 136Xe+209Bi and 136Xe+176Yb reactions estimated using Geant4 Simulation as well as analytical formula support the production of many neutron-rich unknown mass nuclei in the rare-earth region.

Investigating nuclei produced in 9Li +11B reaction

In this contribution, a preliminary analysis of the first part of the experiment S2012 conducted at the ISAC-II facility of Canada’s particle accelerator center TRIUMF in Vancouver will be presented. The experiment aims to study highly clustered structures of nuclei created in multi-nucleon transfer reactions of 9Li radioactive beam on natural boron target (11B and 10B). The main objective of the experiment is to study exotic structures created in neutron-rich 16C nucleus in the range of higher excitation energies. The analysis presented here probes the existence of exotic cluster configurations and the quality of detected results using the invariant mass techniques.

Superheavy nuclei and other exotics – opportunities at SPIRAL2 and S3

The structure of very heavy and superheavy nuclei (SHN) as well as the location of the next proton and neutron shell closures beyond 208Pb is still one of the most intriguing topics in modern nuclear physics [1]. Worldwide competitive, high beam intensities provided by the accelerator facility SPIRAL2 at GANIL which started operation recently, will cover in future all ions up to uranium thanks to the new injector project NEWGAIN. Combined with the separator-spectrometer installation S3 [3], it will provide the instrumental prerequisites for an ambitious science program. Apart from SHN/SHE research, the envisaged physics case at S3 covers, among other, the structure of N=Z nuclei, low energy physics (fundamental properties of the atomic nucleus etc.), interdisciplinary research, atomic physics and reaction studies (fission, deep inelastic reactions etc.). The state of the art of the field is discussed in this paper with an emphasis on the role of the odd particle(s) in odd-even, even-odd and odd-odd nuclei and the consequences for nuclear structure features like K-isomers, trends of single-particle energies as a function of deformation, and the competition of spontaneous fission (SF) and α decay. As an alternative approach to produce heavy and in particular more neutron-rich nuclear species multi-nucleon transfer reactions are briefly discussed as well.

Multinucleon Transfer in 25 MeV/nucleon 86Kr + 64Ni, 124Sn Peripheral Collisions

In this work we investigate multinucleon transfer reaction channels in peripheral collisions between a 86Kr projectile at 25 MeV/nucleon with 64Ni and 124Sn targets. The experimental data of these reactions were obtained with the Momentum Achromat Recoil Separator (MARS) at Texas A&M University in previous works of our group. We extracted and compared experimental mass and momentum per nucleon distributions of ejectiles with a two step model calculation. For the interaction of the projectile with the target, the phenomenological Deep Inelastic Transfer model (DIT) and the microscopic Constrained Molecular Dynamics model (CoMD) were used, both followed by the GEMINI model for the de-excitation of the primary excited projectile-like fragments. Generally, both DIT and CoMD appear to describe the trend of the data for both systems. However, possible further improvements in the models may be necessary. In conjunction with our recent work with a 86Kr beam at 15 MeV/nucleon with a 64Ni target, this study provides further insights into the reaction mechanisms of peripheral collisions in the Fermi energy regime and the production of neutron rich nuclides.

New model based on coupling the Master and Langevin equations in the study of multinucleon transfer reactions

The multinucleon transfer process plays a crucial role for accessing unexplored isotopes far from the β-stable line. Developing reliable models is always one of biggest challenges for understanding the mechanism of the multinucleon transfer (MNT) process and providing accurate predictions. In this work, a new model, combining the Master and Langevin equations (CML), is developed for investigating the mechanism of the MNT reactions. The reaction 136Xe+208Pb is studied. The CML calculations are in rather good agreement with the experimental data. The effects of the incident energy and the entrance angular momentum on the production cross sections are investigated. One intriguing phenomenon is found that the dependence of the incident energy on the production yields in symmetry region is more intense than that for producing trans-target fragments.

Fabrication and characterization of thin [formula omitted]Sn films for heavy-ion nuclear reaction measurements

The fabrication of thin isotopically enriched 120,124Sn targets have been presented. The thin film targets prepared have been used in nuclear physics experiments to apprehend the heavy-ion fusion and multi-nucleon transfer reaction dynamics around the Coulomb barrier. Vacuum evaporation viz. resistive heating technique has been used for the fabrication of the targets with varying areal densities in the range of 50–250 μg/cm2 backed with a carbon layer of ≈20μg/cm2 using a nominal amount of 30 mg isotopically enriched material. The fabricated targets have been characterized using multiple advanced techniques viz. Energy Dispersive X-ray Spectroscopy (EDS), Scanning Electron Microscopy (SEM), and X-ray Diffractometry (XRD). The thickness of the targets has been measured using Rutherford Back-scattering Spectrometry (RBS). The isotopic contamination levels have been ascertained with an in-beam experiment using Heavy Ion Reaction Analyzer at IUAC, New Delhi.

Increasing the rate capability for the cryogenic stopping cell of the FRS Ion Catcher

At the FRS Ion Catcher (FRS-IC), projectile and fission fragments are produced at relativistic energies, separated in-flight, energy-bunched, slowed down, and thermalized in the ultra-pure helium gas-filled cryogenic stopping cell (CSC). Thermalized nuclei are extracted from the CSC using a combination of DC and RF electric fields and gas flow. This CSC also serves as the prototype for the CSC of the Super-FRS, where exotic nuclei will be produced at unprecedented rates making it possible to go towards the extremes of the nuclear chart. Therefore, it is essential to efficiently extract thermalized exotic nuclei from the CSC under high beam rate conditions, in order to use the rare exotic nuclei, which come as cocktail beams. The dependence of the extraction efficiency on the intensity of the impinging beam into the CSC was studied with a primary beam of 238U and its fragments. Tests were done with two different versions of the DC electrode structure inside the cryogenic chamber, the standard 1 m long and a short 0.5 m long DC electrode systems. In contrast to the rate capability of 104 ions/s with the long DC electrode system, results show no extraction efficiency loss up to the rate of 2 × 105 ions/s with the new short DC electrode. This order of magnitude increase of the rate capability paves the way for new experiments at the FRS-IC, including studies of exotic nuclei with in-cell multi-nucleon transfer reactions. The results further validate the design concept of the CSC of the Super-FRS, which was developed to effectively manage beams of even higher intensities.

Helium gas cell with RF wire carpets for KEK Isotope Separation System

We have developed radio-frequency (RF) wire carpets and installed them in a cryogenic helium gas cell to increase the extraction yields of target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions at the KEK Isotope Separation System (KISS). KISS is an on-line isotope separator based on a gas cell system, and has been implemented for nuclear spectroscopy of isotopes approaching the N=126 neutron shell closure below lead and neutron-rich actinides. We optimized the design of the RF wire carpet for efficient ion transport of TLFs from the simulations. We then performed experiments both off-line using rubidium ions from an alkali thermal ion-source in the gas cell, and on-line using TLFs produced by a 136Xe beam impinging upon a 198Pt target system, to confirm the performance expected of the design. We confirmed an increase in the extraction yields of more than an order of magnitude when using the cryogenic He gas cell with RF wire carpets as compared to our typical argon gas cell system with laser resonant ionization. The techniques and knowledge acquired in the development of these RF wire carpets will be applied to new RF wire carpets for use in a large-volume helium gas cell which will be installed at an upgraded KISS facility in the near future.