Unknown Isotopes Research Articles

Observation of New Isotopes in the Fragmentation of ^{198}Pt at FRIB.

Five previously unknown isotopes (^{182,183}Tm, ^{186,187}Yb, ^{190}Lu) were produced, separated, and identified for the first time at the Facility for Rare Isotope Beams (FRIB) using the Advanced Rare Isotope Separator (ARIS). The new isotopes were formed through the interaction of a ^{198}Pt beam with a carbon target at an energy of 186 MeV/u and with a primary beam power of 1.5kW. Event-by-event particle identification of A, Z, and q for the reaction products was performed by combining measurements of the energy loss, time of flight, magnetic rigidity Bρ, and total kinetic energy. The ARIS separator has a novel two-stage design with high resolving power to strongly suppress contaminant beams. This successful new isotope search was performed less than one year after FRIB operations began and demonstrates the discovery potential of the facility which will ultimately provide 400kW of primary beam power.

α decay half-lives of nuclei W, Re, Os, Ir and Pt in the range 157≤A≤193 using the modified generalised liquid drop model (MGLDM)

The α-decay half-lives for the isotopes of nuclei W, Re, Os, Ir and Pt in the range have been studied by using the Modified Generalised Liquid Drop Model (MGLDM). The half-lives predicted for some even–even nuclei by using the deformed Two Potential Approach (TPA) [Comm. Theo. Phys. 74, 055301 (2022)] are considered and included for the comparison. Additionally, we have analysed the α-decay half-lives using eight ℓ-dependent empirical formulae, and compared the results with the experimental data. The standard deviation and the average deviation for by using MGLDM is obtained as 0.6025 and 0.5403, respectively. Also, the results of MGLDM match well with predictions of TPA, with standard deviation of 0.47 and 0.44 respectively. A dip in the half-life curve or a peak in the decay energy curve at 82, a magic neutron number of the daughter nuclei of increases the viability of the calculations. Also, the linear nature of Geiger-Nuttall law, Universal law, the relation connecting and and the New Geiger-Nuttall law helps to calculate the half-lives of newly synthesized and unknown isotopes, making MGLDM more reliable.

Theoretical predictions on α-decay properties of some unknown neutron-deficient actinide nuclei using machine learning * *Supported by the National Natural Science Foundation of China (12035011, 11975167, 11761161001, 11565010, 11961141003, 11905103, 11947211), the National Key R&D Program of China (2018YFA0404403 2016YFE0129300), the Science and Technology Development Fund of Macau (008/2017/AFJ), the Fundamental Research Funds for the Central Universities (22120210138), and the

Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been observed using α-decay spectroscopy [Z. Y. Zhang et al., Phys. Rev. Lett. 122, 192503 (2019); L. Ma et al., Phys. Rev. Lett. 125, 032502 (2020); Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502 (2021)]. In spite of these achievements, some neutron-deficient key nuclei in this mass region are still unknown in experiments. Machine learning algorithms have been applied successfully in different branches of modern physics. It is interesting to explore their applicability in α-decay studies. In this work, we propose a new model to predict the α-decay energies and half-lives within the framework based on a machine learning algorithm called the Gaussian process. We first calculate the α-decay properties of the new actinide nucleus . The theoretical results show good agreement with the latest experimental data, which demonstrates the reliability of our model. We further use the model to predict the α-decay properties of some unknown neutron-deficient actinide isotopes and compare the results with traditional models. The results may be useful for future synthesis and identification of these unknown isotopes.

Effects of nucleus orientation on transfer process and production of unknown neutron-rich isotopes with Z=62–75 in Hg204+Th232 based on the dinuclear system model

Within the framework of the dinuclear system model, the contributions of the constituent parts of the driving potentials in different orientation configurations in the $^{86}\mathrm{Kr}+^{166}\mathrm{Er}$ reaction are investigated. The Coulomb potential plays a predominant role in the change of driving potential among different configurations with mass number ${A}_{1}=52--200$. In the region of ${A}_{1}<52$ and ${A}_{1}>200$, the effects of the nuclear potential increased significantly. This work also studied the multinucleon transfer process of $^{204}\mathrm{Hg}+^{232}\mathrm{Th}$ in tip-to-tip and side-to-side configurations to produce unknown neutron-rich isotopes with $Z=62--75$. In the $^{204}\mathrm{Hg}+^{232}\mathrm{Th}$ reaction, the tip-to-tip configuration accounts for the main contribution to produce unknown neutron-rich isotopes with $Z=62--75$ because of the ``inverse'' quasifission process. The optimal incident energy is 678.1 MeV. Considering the experimental conditions provided by the experiments, there are 29 unknown isotopes whose production rate is greater than one count per day. Especially, the production rates per day of $^{179}\mathrm{Ho}, ^{181,182}\mathrm{Er}, ^{182,183,184}\mathrm{Tm}, ^{186}\mathrm{Yb}, ^{189}\mathrm{Lu}, ^{191,192}\mathrm{Hf}$, and $^{195}\mathrm{Ta}$ are 21, 25, 13, 701, 1217, 29, 94, 29, 102, 29, and 20, respectively. The reaction of $^{204}\mathrm{Hg}+^{232}\mathrm{Th}$ at 678.1 MeV is a potential candidate to produce new neutron-rich nuclei with $Z=62--75$.

A systematic study of α-decay in superheavy nuclei using a Hartree-Fock-Bogoliubov model

Predictions on the alpha decay and spontaneous fission of the superheavy nuclei in the range of Z = 106–118 have been systematically done within the Hartree-Fock-Bogoliubov model and different Skyrme type interactions. A comparison of the results of the current study with experimental values showed good agreement. This study was extended to unknown isotopes in the range of Z = 116–118. The calculated alpha decay half-lives are in the range of 10−5 to 102 s which lie within measurable values. To identify the long-lived isotopes in the mass region, spontaneous fission half-lives were performed using a semi-empirical formula. The results revealed that the isotopes 276,275,274,272,268110, 276,275,273111, 282,280,279112, 281,280,279113, 284,283114, 286115, 289116, 296,295,292,291117, 297,296118, and 295,293,292118 survived fission and had alpha decay mode as the predominant mode of decay which could be synthesized in the laboratory.

Deconvolution of Gamma Ray Spectra Using Singular Value Decomposition of Matrices

Abstract The process of identification of radioactive isotopes using gamma ray spectrum produced by scintillation detectors is a fundamental problem in physics. Military applications also require fast and efficient methods, especially in field conditions, for identifying unknown isotopes. The fundamental problem is the relationship between the observed gamma ray spectrum given by the detector and the real spectrum. This problem can be treated as a mathematical problem. The relationship between the real and the observed spectrum can be described by a linear algebraic equation system. In the previous article Cholesky-decomposition has been applied. In this article one more independent mathematical tool is proposed to solve the linear system efficiently.

The Production of the Isotopes with Z = 98–106 in the Multinucleon Transfer Reaction 238U + 251Cf

The multinucleon transfer process in the reaction 238U + 251Cf is investigated by the dinuclear system model with GEMINI++ code. The time evolution of the fragment probability is studied. For the fragments with larger proton number, the time needed to reach the maximum probability is larger. The isotopic distributions become wider at larger evolution time, and more neutron-rich and proton-rich nuclei can be produced. On the neutron-rich side, the ΔU values becomes higher at larger incident angular momentum, resulting in lower cross sections of neutron-rich nuclei. New neutron-rich isotopes with Z = 98–104 are produced with cross sections larger than 1 nb. Three unknown Db isotopes and two unknown Sg isotopes are generated with cross sections larger than 1 pb.

Identification of Radioactive Isotopes Using Cholesky-Decomposition of Matrices

Abstract The process of identification of radioactive isotopes using gamma ray spectrum produced by scintillation detectors is a fundamental problem in physics. Military applications also require fast and efficient methods, especially in field conditions, for identifying unknown isotopes. The fundamental problem is the relationship between the observed gamma ray spectrum given by the detector and the real spectrum. This problem can be treated as a mathematical problem. The relationship between the real and the observed spectrum can be described by a linear algebraic equation system. In this article an efficient mathematical procedure is proposed to solve this linear system efficiently.

Capture and fission analysis of various superheavy isotopes with ACN = 258–280

The capture and fission analysis of heavy ion induced fusion reactions leading to the formation of Z = 107–111 superheavy nuclei has been carried out. Attempts have been made to analyze the synthesis traits, such as excitation functions, formation probabilities, barrier characteristics etc. The ℓ-summed Wong model provides a decent description of available data on capture (σCap) and fusion-fission (σff) cross-sections and hence is exploited to make relevant predictions for future experiments. The capture and fusion-fission excitation functions are predicted for the least explored region of superheavy nuclei (SHN) i.e. Z = 107–111. The role of mass-asymmetry (η), Coulomb factor (ZPZT), deformation and orientations, Businari-Gallone mass-asymmetry (αBG), fission barrier (Bf) etc is duly explored. The present study concludes that the mass-asymmetric reactions involving 24Mg, 30Si, and 36S projectiles are preferred for the synthesis of unknown isotopes of Z = 107–111. Alternatively, the doubly magic 48Ca-projectile also provides a competing alternative to produce neutron-rich isotopes of the above-mentioned SHN.

Production of neutron-rich isotopes Rf264,266,268,269 by multinucleon transfer reactions based on U238 beam

The production of neutron-rich Rf isotopes in multinucleon transfer reactions is investigated using the dinuclear system model with gemini$++$ code. The reaction $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ is more advantageous to generate neutron-rich Rf isotopes than $^{238}\mathrm{U}+^{249}\mathrm{Bk}$ and $^{238}\mathrm{U}+^{248}\mathrm{Cf}$, because $^{252}\mathrm{Cf}$ has a larger $N/Z$ ratio and neutron number. The influence of incident angular momentum on the production cross sections in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction is investigated. The cross sections of primary products become larger with increasing incident energy, while the final yields of the unknown isotopes at $1.1{V}_{\text{C}}$ are slightly larger than at $1.05{V}_{\text{C}}$ and $1.2{V}_{\text{C}}$. Hence, $1.10{V}_{\text{C}}$ is a suitable incident energy in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction to produce Rf isotopes. Four unknown Rf isotopes, $^{264}\mathrm{Rf}$, $^{266}\mathrm{Rf}$, $^{268}\mathrm{Rf}$, and $^{269}\mathrm{Rf}$, are synthesized in the $^{238}\mathrm{U}+^{252}\mathrm{Cf}$ reaction with cross sections 97.2, 31.1, 0.61, and 0.04 nb, respectively. Considering the beam intensity and thickness of the target, the counts per day of those four unknown isotopes are 2724, 872, 17, and 1, respectively.

Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains

The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories of their decay-in-flight products by using a tracking technique with micro-strip detectors. The proton ($1p$) and two-proton ($2p$) emission processes have been detected in the measured angular correlations "heavy-fragment"+$p$ and "heavy-fragment"+$p$+$p$, respectively. The ground states of the previously unknown isotopes $^{30}$Cl and $^{28}$Cl have been observed for the first time, providing the $1p$-separation energies $S_p$ of $-0.48(2)$ and $-1.60(8)$ MeV, respectively. The relevant systematics of $1p$ and $2p$ separations energies have been studied theoretically in the core+$p$ and core+$p$+$p$ cluster models. The first-time observed excited states of $^{31}$Ar allow to infer the $2p$-separation energy $S_{2p}$ of 6(34) keV for its ground state. The first-time observed state in $^{29}$Ar with $S_{2p} = -5.50(18)$ MeV can be identified either as a ground or an excited state according to different systematics.

α -decay half-lives of superheavy nuclei from a modified generalized liquid-drop model

The \ensuremath{\alpha}-decay half-lives of superheavy nuclei are studied using the generalized liquid-drop model (GLDM) with 1977 nuclear proximity potential proposed by Blocki et al. [Ann. Phys. (NY) 105, 427 (1977)]. The result obtained with the present formalism is compared with the experimental half-lives and half-lives using GLDM. The standard deviation of the present approach is found to be 0.34, which is less than that of GLDM of Royer (0.56). The study is extended to predict the \ensuremath{\alpha} half-lives of some of the unknown isotopes in superheavy region. We hope that the predictions on the \ensuremath{\alpha}-decay half-lives using the present formalism may be helpful in future investigations in this field.

Production of neutron-rich Pt209–212 isotopes based on a dinuclear system model

The production cross sections of new neutron-rich nuclei $^{209\text{--}212}\mathrm{Pt}$ are investigated with multinucleon transfer reactions by the dinuclear system model. It is found that the $^{133}\mathrm{Sn}+^{204}\mathrm{Hg}$ and $^{145}\mathrm{Xe}+^{208}\mathrm{Pb}$ systems are advantageous to produce the neutron-rich nuclei, in which the production cross sections are much higher than those produced in projectile fragmentation reactions. The optimal incident energies for these two systems are about 1.18 and 1.40 times the Coulomb barrier, respectively. The highest cross sections of unknown isotopes $^{209\text{--}212}\mathrm{Pt}$ in the $^{145}\mathrm{Xe}+^{208}\mathrm{Pb}$ reaction are 2.7 nb, 0.4 nb, 8.2 pb, and 2.7 pb, respectively, and those for the $^{133}\mathrm{Sn}+^{204}\mathrm{Hg}$ reaction are 1.7 nb, 0.4 nb, 23.3 pb, and 4.8 pb, respectively.

Discovery of ^{72}Rb: A Nuclear Sandbank Beyond the Proton Drip Line.

In this Letter, the observation of two previously unknown isotopes is presented for the first time: ^{72}Rb with 14 observed events and ^{77}Zr with one observed event. From the nonobservation of the less proton-rich nucleus ^{73}Rb, we derive an upper limit for the ground-state half-life of 81ns, consistent with the previous upper limit of 30ns. For ^{72}Rb, we have measured a half-life of 103(22)ns. This observation of a relatively long-lived odd-odd nucleus, ^{72}Rb, with a less exotic odd-even neighbor, ^{73}Rb, being unbound shows the diffuseness of the proton drip line and the possibility of sandbanks to exist beyond it. The ^{72}Rb half-life is consistent with a 5^{+}→5/2^{-} proton decay with an energy of 800-900keV, in agreement with the atomic mass evaluation proton-separation energy as well as results from the finite-range droplet model and shell model calculations using the GXPF1A interaction. However, we cannot explicitly exclude the possibility of a proton transition between 9^{+}(^{72}Rb)→9/2^{+}(^{71}Kr) isomeric states with a broken mirror symmetry. These results imply that ^{72}Kr is a strong waiting point in x-ray burst rp-process scenarios.

Possibilities of production of transfermium nuclei in complete fusion reactions with radioactive beams

The possibilities of direct production of new isotopes of transfermium nuclei $^{261,263,264}\mathrm{No}$, $^{263,264}\mathrm{Lr}$, $^{263,264,266,268}\mathrm{Rf}$, $^{264,265}\mathrm{Db}$, and $^{267,268,270,272}\mathrm{Sg}$ are studied in various asymmetric hot fusion-evaporation reactions with radioactive beams. The optimal reaction partners and conditions for the synthesis of new isotopes are suggested. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in the $xn$ evaporation channels of the cold and hot complete fusion reactions with the stable beams.

Possibilities of production of neutron-rich Md isotopes in multi-nucleon transfer reactions

The possibilities of production of yet unknown neutron-rich isotopes of Md are explored in several multi-nucleon transfer reactions with actinide targets and stable and radioactive beams. The projectile-target combinations and bombarding energies are suggested to produce new neutron-rich isotopes of Md in future experiments.

Possibilities of production of transfermium nuclei in charged-particle evaporation channels

The possibilities of direct production of the isotopes of transfermium nuclei $^{259,260}\mathrm{Md}, ^{260,261}\mathrm{No}, ^{261\char21{}264}\mathrm{Lr}, ^{264,265}\mathrm{Rf}, ^{264\char21{}268}\mathrm{Db}, ^{266\char21{}269}\mathrm{Sg}, ^{266\char21{}271}\mathrm{Bh}, ^{267\char21{}274}\mathrm{Hs}$, and $^{270\char21{}274}\mathrm{Mt}$ in various asymmetric hot fusion-evaporation reactions are studied. The excitation functions of the formation of these isotopes in the $\ensuremath{\alpha}xn$ and $pxn$ evaporation channels are predicted for the first time. The optimal reaction partners and conditions for the synthesis of new isotopes are suggested. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in the $xn$ evaporation channels of the cold and hot complete fusion reactions.

Possibilities of synthesis of unknown isotopes of superheavy nuclei with charge numbers Z > 108 in asymmetric actinide-based complete fusion reactions

The possibilities of production of new isotopes of superheavy nuclei with charge numbers Z = 109-114 in various asymmetric hot fusion reactions are studied for the first time. The excitation functions of the formation of these isotopes in the xn evaporation channels are predicted and the optimal conditions for the synthesis are proposed. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of the heaviest nuclei obtained in cold and hot complete fusion reactions.

Prospects of heavy and superheavy element production via inelastic nucleus-nucleus collisions – from238U+238U to18O+254Es

Multi-nucleon transfer reactions, frequently termed deep-inelastic, between heavy-ion projectiles and actinide targets provide prospects to synthesize unknown isotopes of heavy actinides and superheavy elements with neutron numbers beyond present limits. The 238 U on 238 U reaction, which revealed essential aspects of those nuclear reactions leading to surviving heavy nuclides, mainly produced in 3 n and 4 n evaporation channels, is discussed in detail. Positions and widths of isotope distributions are compared. It is shown, as a general rule, that cross sections peak at irradiation energies about 10% above the Coulomb barrier. Heavy target nuclei are essential for maximizing cross sections. Experimental results from the 238 U on 248 Cm reaction, including empirical extrapolations, are compared with theoretical model calculations predicting relatively high cross sections for neutron-rich nuclei. Experiments to test the validity of such predictions are proposed. Comparisons between rather symmetric heavy-ion reactions like 238 U on 248 Cm (or heavier targets up to 254 Es) with very asymmetric ones like 18 O on 254 Es reveal that the ones with 238 U as a projectile have the highest potential in the superheavy element region while the latter ones can be advantageous for the synthesis of heavy actinide isotopes. Concepts for highly efficient recoil separators designed for transfer products are presented.

How good are superheavy elementZandAassignments?

Proton number, Z , and mass number, A , assignments for newly discovered heavy element nuclides have historically been made by observing α decay to a daughter with well-established Z and A , and then observing the well-know decay of that daughter. For all of the new superheavy element isotopes observed in 48 Ca irradiations of actinide targets, this correlation technique has not been possible, because the α-decay chains end in spontaneous fission of previously unknown isotopes. Consequently, Z and A assignments have been made by less-direct means. The superheavy element Z and A assignment methods are summarized, and possibilities for how they may be incorrect are explored. While it is highly likely that most of the superheavy element Z and A assignments are correct, there is a real need for a direct proof.