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This note advertises a simple necessary condition for optimality that any list N ↦ vx(N) of computer-generated putative lowest average pair energies vx(N) of clusters that consist of N monomers has to satisfy whenever the monomers interact with each other through pair forces satisfying Newton's "action equals re-action." These can be quite complicated, as, for instance, in the TIP5P model with five-site potential for a rigid tetrahedral-shaped H2O monomer of water, or as simple as the Lennard-Jones single-site potential for the center of an atomic monomer (which is also used for one site of the H2O monomer in the TIP5P model, which in addition has four peripheral sites with Coulomb potentials). The empirical usefulness of the necessary condition is demonstrated by testing a list of publicly available Lennard-Jones cluster data that have been pooled from 17 sources, covering the interval 2 ≤ N ≤ 1610 without gaps. The data point for N = 447 failed this test, meaning the listed 447-particle Lennard-Jones cluster energy was not optimal. To implement this test for optimality in search algorithms for putatively optimal configurations is an easy task. Publishing only the data that pass the test would increase the odds that these are actually optimal, without guaranteeing it, though. [ABSTRACT FROM AUTHOR]

A method for calculating the forces and moments of friction forces arising between two colliding nuclei with a nonzero impact parameter is considered. At this stage of the work, it is assumed that colliding nuclei remain spherical throughout the entire collision process. The collision process of spherical atomic nuclei is simulated taking into account their gradual inclusion in rotation around their own axes. It is shown that it takes time about s from the moment of the transition of the system through the Coulomb barrier to the stop of the relative rotation of colliding nuclei. It is proposed to consider the stopping of radial motion and relative rotation of colliding nuclei as conditions for capturing the projectile nucleus by the target nucleus. That is, at the moment of capture, the system should behave like a rigid rotating dumbbell. Comparison of the calculation results of the capture cross sections with the experimental data shows a good predictive power of the considered approximate model in the case of a strongly asymmetric reaction of Pb (for all reaction energies) and in the case of high-energy reactions of Pb and Pb. [ABSTRACT FROM AUTHOR]

Disorder-induced heating (DIH) prevents ultracold neutral plasma into the electron strong coupling regime. Here, we propose a scheme to suppress electronic DIH via optical lattice. We simulate the evolution dynamics of ultracold neutral plasma constrained by three-dimensional optical lattice using the classical molecular dynamics method. The results show that for experimentally achievable conditions, electronic DIH is suppressed by a factor of 1.3, and the Coulomb coupling strength can reach 0.8, which is approaching the strong coupling regime. Suppressing electronic DIH via optical lattice may pave a way for the research of electronic strongly coupled plasma. [ABSTRACT FROM AUTHOR]

The influence of saturation property of cold nuclear matter on the parameterization process of fusion barriers are systematically studied using the double-folding procedure supplemented with the effect of Pauli repulsive interaction between two colliding nuclei. We obtain simple analytical expressions for calculating the fusion barrier position R B , height V B and curvature ħ ω B with and without the repulsion effects to evaluate the heavy-ion fusion cross sections. We have studied 90 heavy-ion fusion reactions with 64 ≤ Z 1 Z 2 ≤ 1520 for charge product of the projectile and the target nuclei. The obtained results reveal that our parameterized formulae can reproduce the exact and experimental values of the fusion barrier characteristics with acceptable accuracy for the selected mass range. We calculate the theoretical values of the fusion cross sections using the parameterized values of R B , V B and ħ ω B . The comparison between the calculated and measured values of the fusion cross section at energies near and above the Coulomb barrier validates the quality of the presently obtained formulae. A discussion is also presented about the validity of the previous pocket formulae for fusion barriers in our selected mass range. [ABSTRACT FROM AUTHOR]

The low-lying nuclear structure of even-even Zn isotopes ranging from 62 Zn to 70 Zn has been comprehensively examined through large scale shell model calculations. These calculations encompassed the f 5 / 2 p 3 / 2 , 1 / 2 g 9 / 2 (fpg) model space without any truncation, employing 56 Ni as an inert core. Two different effective interactions, JUN45 and jj44b, were utilized in these calculations. Various critical observables, including excitation energies, reduced transition strengths, and electric quadrupole moments, were computed and then evaluated in the context of existing experimental data. The configurations of the resulting wave functions were also thoroughly analyzed. Furthermore, occupation probabilities for distinct single-particle orbitals were determined, with particular attention given to the pivotal role of the g 9 / 2 orbital in elucidating the nuclear structure of heavy Zn isotopes. Additionally, rotational invariants were calculated for the ground state, shedding light on a prolate deformation in 62 Zn and 64 Zn, while suggesting moderate prolate-triaxial excitations in 66 Zn, 68 Zn, and 70 Zn. These findings hold significant relevance for interpreting the intriguing outcomes of sub-barrier Coulomb excitation experiments, offering invaluable insights into the static electromagnetic properties of the nucleus through a model-independent approach. [ABSTRACT FROM AUTHOR]

The barrier penetrability, decay constant and decay half-life of 1-n halo nuclei 11Be, 15,17,19C, 22N, 23O, 24,26F, 29,31Ne, 34,37Na, 35,37Mg, and 55Ca; and 2-n halo nuclei 22C, 27,29F, 34Ne, 36Na, and 46P from Z = 127 – 132 parents were calculated within the framework of the Coulomb and proximity potential model by calculating the Q-values using the finite-range droplet model. A comparison between the decay half-lives is made by considering the halo candidates as a normal cluster and as a deformed structure with a rms radius. Neutron shell closure at 190, 196, 198, 200, 204, and 208 are identified from the plot of decay half-lives versus the neutron number of daughter nuclei (NP). The calculation of alpha decay half-life and spontaneous decay half-life showed that the majority of the parent nuclei survive spontaneous fission and decay through alpha emission. The Geiger - Nuttall plots of log10 T1/2 versus Q−1/2 and universal plots of log10 T1/2 versus − ln P for the emission of all 1-n and 2-n halo nuclei from the parents considered here are linear and show the validity of Geiger - Nuttall law in the case of decay of halo nuclei from superheavy elements. [ABSTRACT FROM AUTHOR]

Nuclear fusion reactions, at energies, far below the Coulomb barrier play a significant role in the synthesis of light elements in the primordial nucleosynthesis as well as in the interior of compact stellar objects. Many different kinds of nuclear reactions are occurring simultaneously inside the stellar core depending upon the density and temperature conditions of the nuclear plasma along with other relevant parameters of these stars. Nuclear fusion reactions in the energy range (E ∼ 1 eV to few keV) can be explained successfully by quantum mechanical tunneling through the mutual Coulomb barrier of interacting nuclei. The measurement of the cross-sections at extremely low energy is quite difficult because of the larger width of the Coulomb barrier, which results in a very small value of the reaction cross-section. Hence, any improvement in the data on astrophysical S-factors for the light nuclei fusion may give a better picture of the elemental abundance in nucleosynthesis. In this work, we have theoretically investigated the energy dependence of fusion cross-sections and astrophysical S-factors for fusion reaction of light nuclei like D-D and p11B using complex Gaussian nuclear potential with adjustable depth and range parameters plus the mutual Coulomb interaction of the interacting nuclei. Numerical computation of the observables is done in the framework of the selective resonant tunneling model approach. The results of our calculation are compared with those found in the literature. [ABSTRACT FROM AUTHOR]

The new analytical barrier penetration formula proposed by Li et al. [Int. J. Mod. Phys. E 19 (2010) 359] for potential barriers containing a long-range Coulomb interaction is adopted in the empirical coupled-channel (ECC) model for calculating fusion cross-sections. As compared with the Hill–Wheeler (HW) formula based on the parabolic approximation, this formula is more appropriate for the barrier penetration with incident energies much lower than the Coulomb barrier. The calculated results show that the ECC model with the new barrier penetration formula can describe the fusion cross-section data well, especially for light systems at energies much lower than the Coulomb barrier. Then the systematics of the difference between the ECC calculation with the new penetration formula and that with the HW formula is investigated. The results show that the difference between the results with the HW formula and the new penetration formula is less than one order of magnitude at E c.m. > 0. 8 9 V B . [ABSTRACT FROM AUTHOR]

This article is a new edition of the review published six years ago by the same auhors [Eur. Phys. J. A 54, (2017) 218]. It includes additionally the most recent and significant results obtained in the field of heavy-ion fusion near and below the Coulomb barrier, which have been important for the advance of our knowledge. In particular, we present a selection of recent findings concerning the fusion dynamics of light systems, which is relevant for astrophysics, and moreover recent information obtained from measurements involving heavy-ion exotic beams. With respect to the previous paper, the description of relevant set-ups and methods is done in a dedicated Section. Recent advances obtained in the field of near and sub-barrier heavy-ion fusion reactions are reported. Early data on sub-barrier fusion taught us that cross sections strongly depend on the low-energy collective modes of the colliding nuclei, and on couplings to transfer channels. The coupled-channels model has been successful in the interpretation of the experiments, and fusion barrier distributions may yield the fingerprint of the relevant coupled channels. Far below the barrier, the slope of the excitation function keeps increasing in many cases and standard calculations over-predict the cross sections. This was named a hindrance phenomenon whose physical origin is a matter of debate. Recent theoretical developments suggest that hindrance may be a consequence of the Pauli exclusion principle. Hindrance has far-reaching consequences in astrophysics where the fusion of light systems determines stellar evolution during the carbon and oxygen burning stages. [ABSTRACT FROM AUTHOR]

This study uses a spring‐block model and rate and state friction to simulate experiments conducted in a double direct‐shear apparatus on carbonate fault gouge (Scuderi et al., 2017, https://doi.org/10.1016/j.epsl.2017.08.009) and on shale bearing rock (Scuderi & Collettini, 2018, https://doi.org/10.1029/2018jb016084). Both sets of experiments used the same loading protocol and injected pore fluid under creep conditions. When velocity strengthening rate and state friction is used to simulate the experiments on the carbonate fault gouge the results agree well with the observed onset of tertiary creep in the experiment. Thus, the simulation reinforces the observation that pore fluid injection can induce rapid slip even when the friction relation is velocity strengthening. The rate and state framework provides an interpretation alternative to the standard one of the Mohr's circle moving to the left as pressure increases. In the rate and state framework, the friction coefficient must increase with pore pressure increase. The shale has a low nominal friction coefficient (0.28) and is much more velocity strengthening than the carbonate. The simulation agrees with the observations that increases in pore pressure induce an increase in slip velocity but the magnitudes reach only about 100 microns/s by the end of the experiment. The simulation for the shale also agrees well with the magnitude of the observed displacement at the end of the experiment but observed displacement is increasing much more rapidly the calculated. Although the calculations agree well with features of the observations near failure, the overall curves of displacement and velocity are significantly different. Plain Language Summary: Recent industrial processes that involve injection of fluids, such as geothermal stimulation, disposal of waste water from hydraulic fracturing and carbon sequestration, have induced seismicity that has caused concern and resulted in discontinuation of the activity. Although field experiments are ultimately necessary to establish the conditions for safe operation, laboratory experiments on fluid injection provide a more controlled environment that can yield insight into the basic physical mechanisms. Numerical simulations can test the models for such mechanisms and provide a basis for extrapolation to field conditions. This study uses a simple model and a well‐established formulation of rock friction to simulate injection experiments on two types of fault zone material. For one, the simulation agrees well with the experiment and reinforces the observation that fluid injection can induce rapid slip for frictional behavior thought to suppress it. The good agreement suggests another interpretation for the failure process and allows simulation conditions not tested in the experiments. For the other material, the simulations are consistent with the observation that the pressure increases do not induce large slip velocities. Nevertheless, differences between the measured and calculated curves suggest that mechanisms other than those included in the simple model are significant. Key Points: Simulations corroborate the observation that increase in pore fluid pressure can induce rapid slip in a velocity strengthening materialRate and state friction suggests an alternative explanation for the approach to failure than one based on the usual Coulomb conditionSimulations demonstrate the significance of the effect of normal stress changes on the state variable [ABSTRACT FROM AUTHOR]

The scaling of reaction yields in light ion fusion to low reaction energies is important for our understanding of stellar fuel chains and the development of future energy technologies. Experiments become progressively more challenging at lower reaction energies due to the exponential drop of fusion cross sections below the Coulomb barrier. We report on experiments where deuterium-deuterium (D-D) fusion reactions are studied in a pulsed plasma in the glow discharge regime using a benchtop apparatus. We model plasma conditions using particle-in-cell codes. Advantages of this approach are relatively high peak ion currents and current densities (0.1 to several A/cm2) that can be applied to metal wire cathodes for several days. We detect neutrons from D-D reactions with scintillator-based detectors. For palladium targets, we find neutron yields as a function of cathode voltage that are over 100 times higher than yields expected for bare nuclei fusion at ion energies below 2 keV (center of mass frame). A possible explanation is a correction to the ion energy due to an electron screening potential of 1000 ± 250 eV, which increases the probability for tunneling through the repulsive Coulomb barrier. Our compact, robust setup enables parametric studies of this effect at relatively low reaction energies. [ABSTRACT FROM AUTHOR]

Photoelectron spectroscopy and theoretical investigations have been performed to systematically probe the intrinsic electronic properties of [Mo6X14]2− (X = halogen). All three PE spectra of gaseous [Mo6X14]2− (X = Cl, Br, I) dianions, which were generated by electrospray ionization, exhibit multiple resolved peaks in the recorded binding energy range. Theoretical investigations on the orbital structure and charge distribution were performed to support interpretation of the observed spectra and were further extended onto [Mo6F14]2−, a dianion that was not available for the experimental study. The measured adiabatic (ADE) and vertical detachment energies (VDE) for X = Cl–I were well reproduced by density functional theory calculations (accuracy ∼0.1 eV). Corresponding ADE/VDE values for the dianions were found to be 1.48/2.13 (calc.) and 2.30/2.65, 2.30/2.62, and 2.20/2.42 eV (all expt.) for X = F, Cl, Br, and I, respectively, showing an interesting buckled trend of electron binding energy (EBE) along the halogen series, i.e., EBE (F) ≪ EBE (Cl) ∼ EBE (Br) > EBE (I). Molecular orbital analyses indicate different mixing of metal and halogen atomic orbitals, which is strongly dependent on the nature of X, and suggest that the most loosely bound electrons are detached mainly from the metal core for X = F and Cl, but from halide ligands for X = Br and I. The repulsive Coulomb barrier (RCB), estimated from the photon energy dependent spectra, decreases with increasing halogen size, from 1.8 eV for X = Cl to 1.6 eV for X = I. Electrostatic potential modeling confirms the experimental RCB values and predicts that the most favorable electron detaching pathway should lie via the face-bridging halide ligands. [ABSTRACT FROM AUTHOR]

The dependence of the properties of the fission fragments formed both in the fusion-fission and fast fission processes on the angular momentum still remains very unclear from an experimental as well as theoretical point of view. To study the properties of fast fission fragments of preactinide nuclei as function of the interaction energy and introduced angular momentum, the mass-energy distributions of Pb fission fragments formed in the Sm reaction at energies above the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET at the Ca ions' energies of 212, 231, 244, and 277 MeV. The mass-energy distributions of the fast fission fragments have been extracted by subtracting the mass-energy matrices corresponding to the compound nucleus fission from those of all measured fissionlike events. The asymmetric fragments with masses 76 and 108 u were found to be the most probable in the fast fission of Pb. With increasing Ca energy from 231 to 277 MeV the mass distributions of fast fission fragments change weakly, whereas an increase in the TKE is about 20 MeV. The properties found for the fast fission fragments indicate the incomplete mass relaxation and not full energy dissipation. [ABSTRACT FROM AUTHOR]

We perform a comprehensive analysis of complete fusion cross section data with the aim to derive, in a completely data-driven way, a model suitable to predict the integrated cross section of the fusion between light-to-medium mass nuclei at above barrier energies. To this end, we adopted a novel artificial intelligence approach, based on a hybridization of genetic programming and artificial neural networks, capable to derive an analytical model for the description of experimental data. The approach enables to perform a global search for computationally simple models over several variables and a considerable body of nuclear data. The derived phenomenological formula can serve to reproduce the trend of fusion cross section for a large variety of light to intermediate mass collision systems in an energy domain ranging approximately from the Coulomb barrier to the onset of multi-fragmentation phenomena. [ABSTRACT FROM AUTHOR]

Current–voltage characteristics of a quantum dot in double-barrier configuration, as formed in the nanoscale channel of silicon transistors, were analyzed both experimentally and theoretically. Single electron transistors (SET) made in a SOI-FET configuration using silicon quantum dot as well as phosphorus donor quantum dots were experimentally investigated. These devices exhibited a quantum Coulomb blockade phenomenon along with a detectable effect of variable tunnel barriers. To replicate the experimental results, we developed a generalized formalism for the tunnel-barrier dependent quantum Coulomb blockade by modifying the rate-equation approach. We qualitatively replicate the experimental results with numerical calculation using this formalism for two and three energy levels participated in the tunneling transport. The new formalism supports the features of most of the small-scaled SET devices. [ABSTRACT FROM AUTHOR]

Inter-University Accelerator Centre (IUAC) came into existence as Nuclear Science Centre in 1984. A 15UD Pelletron accelerator was installed and it started delivering accelerated charged particle beams in 1991. Various experimental research facilities were set up in parallel at the Centre. All these facilities have been and are being extensively used by scholars and researchers from various universities and institutes in India. Research activities in nuclear physics, materials science and other inter-disciplinary fields are the main thrust at the laboratory. Nuclear physics research carried out at IUAC has made an indelible mark in the understanding of nuclear structure and nuclear reaction dynamics using heavy ion beams at near and above Coulomb barrier energy region. This review article presents the details of the various experimental facilities and highlights of research contributions in nuclear reactions and nuclear structure, spanning three decades. [ABSTRACT FROM AUTHOR]

The role of closed and deformed proton and neutron shells in the fission of Cf and Fm nuclei at excitation energies from 40 to 56 MeV is studied. The mass–energy distributions of fission fragments of these nuclei formed in the Th and U reactions at projectile-ion energies close to the Coulomb barrier are measured by means of the CORSET time-of-flight spectrometer. It is shown that, in all of the reactions under study, an enhanced yield of fragments in the mass region around 100 a.m.u. is due to the effect of the deformed proton shell. A manifestation of a supershort mode is found in the fission of Fm at the compound-nucleus excitation energy of 40 MeV. [ABSTRACT FROM AUTHOR]

The present evaluation of currently known nine nuclides of A=231: (231Rn, 233Fr, 231Ra, 231Ac, 231Th, 231Pa, 231U, 231Np and 231Pu) represents an update and revision of previous A=231 evaluation by 2013Br04. All the known decay and reaction data are evaluated, with recommended properties given in the Adopted Levels, Gammas datasets, for gamma-ray energies, photon branching ratios, level half-lives, spins, parities, transition probabilities, and configuration assignments. For 231Rn, only an identification of the nuclide has been made without an experimental determination of its half-life. For 231Fr, no excited states are known. About 30 levels in 231Ra up to 1774 keV excitation are known only from β − decay of 231Fr with level half-lives determined for five excited states. For 231Ac, excited states up to 3122 keV are known from β − decay, (t, α), and fragmentary information for high-spin levels from two heavy-ion reaction studies, with lifetimes of excited states measured for five levels. Extensive structure and rotational band information for 231Th is available for a large number of levels up to 1714 keV from β − and α decays, (n, γ) thermal and resonance, single-particle transfer reactions (d,p), (d,t) and (3He, α), with limited data for high-spin levels from one secondary reference, and half-lives available for five excited states. Very detailed structure data are available for 231Pa up to 2139 keV from β −, ε and α decays, (α ,t), (d,d′) and high-spin data from heavy-ion Coulomb excitation and (p,2n γ) reaction, with level half-lives known for 34 excited states, mostly deduced by evaluators from transition probabilities determined in Coulomb excitation. Only eight excited states are known in 231U up to 1268 keV from ε and α decays, with no data for half-lives of excited states. For 231Np and 231Pu, only the ground-state is known from α decays, with a tentative level at 324 keV in 231Pu. Measurements of nuclear rms charge radius and isotope shifts for 231Ra have been made by 2018Ly01, and that for rms charge radius for 231Fr by 2014Bu06. 235U is a well known nuclide for nuclear structure and reactor applications. There have been a large number of studies of its alpha decay to levels in 231Th, including some recent ones such as 2018Ma03 and 2017Le03, yet evaluators' analysis of the decay scheme suggests that, while α -particle transitions are well established, but several issues still remain about intricacies of gamma-ray and conversion electron spectroscopy which need to be resolved through dedicated experiments for a complete understanding of the decay scheme characteristics, although, this sort of research project would seem a challenging spectroscopic problem. As commented in individual datasets for other decays, important spectral information is lacking for most of the decay schemes, with almost no information available for some of these, resulting in many incomplete decay schemes in A=231 mass chain. [ABSTRACT FROM AUTHOR]

We report a joint benchmark study on the electronic stability of closo-dodecaborate [B12H12]2− employing negative ion photoelectron spectroscopy and high level electronic structure methods. The photoelectron spectra of [B12H12]2−, measured at 266, 193, and 157 nm, yield the Adiabatic and Vertical Detachment Energies (ADE and VDE) of this dianion at 0.93 ± 0.05 eV and 1.15 ± 0.05 eV, respectively, along with a ∼3 eV Repulsive Coulomb Barrier (RCB) against electron detachment. Theoretical calculations at various levels of electronic structure theory confirm the high stability of this dianion. The ADE and VDE values calculated at the coupled cluster with single, double and a perturbative estimate of triple excitations/aug-cc-PVQZ level are 0.92 and 1.16 eV, in excellent agreement with the experimental benchmark values. The comparison between the experimental and the theoretical values obtained at different levels of theory indicate that the PBE0 density functional represents a cost-effective method of sufficient accuracy to describe the molecular properties of this dianion and associated compounds. The theoretical RCB was modeled after the electrostatic potential (ESP) and point charge method (PCM) along three different detachment pathways, viz., along the B–H bond, perpendicular to a B–B bond, and normal to a B–B–B triangle. It was found that detachment of the electron along the B–H bond is preferred, as this pathway is associated with RCBs between 2.3 eV (PCM) and 3.3 eV (ESP), values that bracket the experimental estimate of ∼3 eV. [ABSTRACT FROM AUTHOR]

A new form of potential is used to treat the optical model unequivocally for the analysis of scattering results of the 58Ni + 27Al system. The phenomenological optical potential is formed with the Ginocchio potential for analysis near the Coulomb barrier. Theoretical calculations explain the experimental outcomes over a wide range of colliding energies, and hence exhibit threshold anomaly. An inbuilt non-trivial behaviour in the formulation near the Coulomb barrier position is found essential for a successful explanation of the experimental results. [ABSTRACT FROM AUTHOR]

In organic solar cells (OSCs), the lower dielectric constant of organic semiconductor material induces a strong Coulomb attraction between electron–hole pairs, which leads to a low exciton separation efficiency, especially the charge transfer (CT) state. The CT state formed at the electron‐donor (D) and electron‐acceptor (A) interface is regarded as an unfavorable property of organic photovoltaic devices. Since the OSC works in a nonzero temperature condition, the entropy effect would be one of the main reasons to overcome the Coulomb energy barrier and must be taken into account. In this review, the present understanding of the entropy‐driven charge separation is reviewed and how factors such as the dimensionality of the organic semiconductor, energy disorder effect, the morphology of the active layer, are described, as well as how the nonequilibrium effect affects the entropy contribution in compensating the Coulomb dissociation barrier for CT exciton separation and charge generation process. The investigation of the entropy effect on exciton dissociation mechanism from both theoretical and experimental aspects is focused on, which provides pathways for understanding the underlying mechanisms of exciton separation and further enhancing the efficiency of OSCs. [ABSTRACT FROM AUTHOR]

To transport a spacecraft to distances far beyond the solar heliosphere and around the planets of other stars will require advanced space propulsion systems that go beyond the existing technological state of the art. The release of fusion energy from the interaction of two low mass atomic nuclei that are able to overcome the Coulomb barrier offers the potential for ∼1011J/g specific energy release and implies that robotic missions to the nearby stars to distances of ∼5–10 ly may be possible in trip durations of the order of ∼50–100 years, travelling at cruise speeds of the order of ∼0.05–0.15 c. Such missions would be characterised with ∼kN-MN thrust levels, ∼GW-TW jet powers, ∼kW/kg-MW/kg specific powers. One of the innovative methods by which fusion reactions can be ignited is via the impingement of laser beams onto an inertial confinement fusion capsule, imploding it to a thermonuclear state. This paper gives an overview of the physics of inertial confinement fusion and the interaction of a laser beam with a capsule to include the simulation of a 1D particle-in-cell code calculation to illustrate the effects. In the application to deep space missions, various spacecraft concepts from the literature are discussed, and the range of values assumed for the pulse frequency, burn fraction and areal density appropriate for the mission are presented. It is concluded that advanced space propulsion via inertial confinement fusion is a plausible part of our future, provided that experimental validation of ignition is on the horizon and numerical models for feasibility concepts are developed to high fidelity and on a consistent basis. [ABSTRACT FROM AUTHOR]

The role of nucleon transfer channel coupling on the sub-barrier fusion excitation function has been elusive. Many studies have attributed a significant sub-barrier fusion cross-section enhancement over one-dimensional barrier penetration model (1d-BPM) calculation to nucleon transfer couplings. However, several systems exhibit no such enhancement besides having positive Q-value nucleon transfer channels.The objective is to delve into the role of coupling to various internal degrees of freedom on the fusion excitation functions in interactions of 19 F with 64 , 68 Zn. Fusion cross-section measurements are performed at energies ∼ 20 % above to ∼ 15 % below the Coulomb barrier using Heavy Ion Reaction Analyzer (HIRA) at Inter-University Accelerator Center (IUAC), New Delhi. Coupled-channel (CC) calculations, including coupling to vibrational states of 64 , 68 Zn, rotational states of 19 F, and nucleon transfer channels are performed. Cross-sections for various transfer channels are calculated to speculate their coupling effects on the fusion excitation functions. The results are compared on a reduced scale with neighboring systems involving 19 F and 18 O as the projectile. The sub-barrier fusion cross-sections of 19 F + 64 , 68 Zn systems are enhanced by orders of magnitude compared to the corresponding 1d-BPM calculations. CC calculations performed with CCFULL, including coupling to collective excitations of reactants and pair transfer channel, failed to reproduce the experimental fusion cross-sections. GRAZING calculations show large one nucleon transfer cross-sections relative to other channels for the two systems. CCDEF calculation show that inclusion of coupling to one proton transfer channel is necessary to reproduce the experimental data for both systems. [ABSTRACT FROM AUTHOR]

We have constructed empirical formulae for the fusion and interaction barriers using a large number of experimental values chosen randomly from the literature available till date. The obtained fusion barriers have been compared with different model predictions based on the proximity, Woods–Saxon and double folding potentials along with several empirical formulas, time-dependent Hartree–Fock theories and experimental results. The comparison allows us to find the best model, which is nothing but the present empirical formula only. Most remarkably, the fusion barrier and radius show excellent consonance with the experimental findings for the reactions meant for the synthesis of superheavy elements also. Furthermore, it is seen that substitution of the predicted fusion barrier and radius in classic Wong formula (Wong, Phys. Rev. Lett.31:766 (1973) for the total fusion cross-sections agrees very well with the experiments. Similarly, current interaction barrier predictions have also been compared well with a few experimental results available and Bass potential model meant for the interaction barrier predictions. Importantly, the present formulae for the fusion as well as interaction barrier will have practical implications in carrying out physics research near the Coulomb barrier energies. Furthermore, the present fusion barrier and radius provide us with a good nucleus–nucleus potential which is useful for numerous theoretical applications. [ABSTRACT FROM AUTHOR]

Nuclear fusion reactions at low energies (E ∼ 1 eV to few KeV) are crucial for the primordial nucleosynthesis of light elements. Nuclear fusion reactions in this energy window can be understood fruitfully in terms of quantum mechanical tunneling through the mutual Coulomb barrier of interacting nuclei. In this work, we studied the fusion cross-section, σ and astrophysical S-factor in the selective resonant tunneling model (SRTM) approach for the p + 1 5 N and α + 1 2 C nuclear fusion reactions. We used space varying complex Gaussian type nuclear potential here. The quantum mechanical findings of the fusion cross-section, σ and S-factor are in excellent agreement with the experimentally observed results found in the literature. The improved value of astrophysical S-factors for light nuclei may give a more clear picture of the elemental abundance in primordial nucleosynthesis. [ABSTRACT FROM AUTHOR]

In this work, the stability of a shield tunnel face under pore water pressures is examined by combining the non-linear Mohr-Coulomb failure criterion in the framework of the kinematic approach of limit analysis. The non-linear Mohr-Coulomb failure criterion represented by the tangent technique in combination of the pore water pressure distribution calculated by the mesh dividing optimization technology are incorporated into the 3D rotational failure mechanism to assess the critical support pressure of a tunnel face for the first time. Based on the proposed method, parametric studies are performed by giving design charts to study the effect of model parameters on the calculated critical support pressure. In these charts, comparisons with results from the linear Mohr-Coulomb failure criterion are used to verify the proposed method. Finally, the influence of the non-linear coefficient on the feature of the 3D rotational failure mechanism is presented. [ABSTRACT FROM AUTHOR]

We investigate the influence of strong dichromatic laser fields (i.e., 1 ω - 2 ω and 1 ω - 3 ω ) with high-frequency limit on the cross sections of deuteron-triton (DT) fusion in Kramers-Henneberger (KH) frame. We focus on the transitions of phase-dependent effects depending on a dimensionless quantity n d , which equals the ratio of the quiver oscillation amplitude to the geometrical touching radius of the deuteron and triton as defined in our previous research. Theoretical calculations show that the angle-dependent as well as phase-dependent Coulomb barrier penetrabilities can be enhanced in dichromatic intense fields, and the corresponding angle-averaged penetrabilities and the fusion cross sections increase significantly compared with field-free case. Then, we investigate the effects of the two beams with different intensities. Moreover, we find that there are twice shifts of the peak values for the phase-dependent cross sections with the increase of n d . The reason for the first shift is the angle-dependent effects for sub-barrier fusion, while the second shift is due to the accumulation of over-barrier fusion, these mechanisms are analyzed in detail in this paper. [ABSTRACT FROM AUTHOR]

The radioactive decay probabilities of various proton halo (p-halo) nuclei from parent isotopes in the superheavy (SH) region, Z = 115–120, were analysed by taking the Coulomb and proximity potential as the interacting barrier. The nuclear decay half-lives ( t 1 / 2 ) , barrier penetrability and various other attributes for the decay of p-halo nuclei such as 8 B, 9 C, 11 , 12 N, 17 F, 17 , 18 Ne, 23 Al and 26 , 27 , 28 P from the isotopes 261 -- 278 115 , 264 -- 279 116 , 267 -- 284 117 , 271 -- 283 118 , 274 -- 288 119 and 277 -- 285 120 are determined. From the determined decay lifetime values, it is understood that most of the p-halo decays are probable. The error bars in the halo radius are incorporated for the nuclear decay half-life for these p-halo nuclei. Moreover, the effects of shell closure in the daughter and the parent nuclei are also clear from the plots of calculated decay half-lives vs. neutron number of the daughter nuclei. Peak and dip in the plots show the closed shell effects of the parent and daughter nuclei respectively. We found the closed shell effect of the parent at N p ∼ 152 and closed shell effect of the daughter nuclei at N d ∼ 132 , 142 . Further, we have analysed the Geiger–Nuttall (GN) plots of logarithmic half-life time vs. Q - 1 / 2 and the universal curve of logarithmic half-life time against negative logarithm of the barrier penetrability for the chosen p-halo decay from the SH parents, Z = 115 -- 120 and are found to be linear. Also, we can find that the addition of proximity potential does not make any notable variation in the behaviour of the Geiger–Nuttall plots. Hence GN law is also applicable to p-halo decay. [ABSTRACT FROM AUTHOR]

We study electronic image states around a metallic nanoring and show that the interplay between the attractive polarization force and a repulsive centrifugal force gives rise to Rydberg-like image states trapped several nanometers away from the surface. The nanoring is modeled as a perfectly conducting isolated torus whose classical electrostatic image potential is derived analytically. The image states are computed via a two-dimensional finite-difference scheme as solutions of the effective Schrödinger equation describing the outer electron subject to this image potential. These findings demonstrate not only the existence of detached image states around nanorings but allow us also to provide general criteria on the ring geometry, i.e., the aspect ratio of the torus, that need to be fulfilled in order to support such states. [ABSTRACT FROM AUTHOR]

Professor Dr. Jens Volker Kratz, a distinguished experimental nuclear chemist, passed away on February 11, 2024, at the age of 79. He was known for his work in the field of the heaviest elements. Born in Jena, Germany, in 1944, he obtained his Ph.D. in nuclear spectroscopy and fission yields of short-lived isotopes. He worked at various institutions, including the Lawrence Berkeley Laboratory and the Society for Heavy Ion Research, and joined the faculty of Johannes Gutenberg University Mainz in 1982. His research focused on heavy-ion reactions, transactinide elements, and actinides in the environment. He received recognition for his scientific work, including the Otto-Hahn Prize in 1998. After retiring in 2009, he remained active and published a textbook. Professor Kratz's dedication to science and warm-heartedness will be missed. [Extracted from the article]

The fabrication of thin isotopically enriched 120 , 124 Sn 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 μ g/cm 2 backed with a carbon layer of ≈ 20 μ g/cm 2 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. • Nuclear reaction measurements around the Coulomb barrier energies. • Vacuum evaporation technique for the fabrication of thin tin films. • Advanced characterization techniques for characterization of the fabricated samples. • Uniform, homogeneous films free of any heavy elemental impurities fabricated. • Isotopic contamination levels ascertained using online experiment. [ABSTRACT FROM AUTHOR]

A reliable description of nuclear fusion reactions in inner layers of white dwarfs and envelopes of neutron stars is important for realistic modelling of a wide range of observable astrophysical phenomena from accreting neutron stars to Type Ia supernovae. We study the problem of screening of the Coulomb barrier impeding the reactions by a plasma surrounding the fusing nuclei. Numerical calculations of the screening factor are performed from the first principles with the aid of quantum-mechanical path integrals in the model of a one-component plasma of atomic nuclei for temperatures and densities typical for dense liquid layers of compact degenerate stars. We do not rely on various quasi-classic approximations widely used in the literature, such as factoring out the tunnelling process, tunnelling in an average spherically symmetric mean-force potential, usage of classic free energies and pair correlation functions, linear mixing rule, and so on. In general, a good agreement with earlier results from the thermonuclear limit to Γ ∼ 100 is found. For a very strongly coupled liquid 100 ≲ Γ ≤ 175, a deviation from currently used parametrizations of the reaction rates is discovered and approximated by a simple analytic expression. The developed method of nuclear reaction rate calculations with account of plasma screening can be extended to ion mixtures and crystallized phases of stellar matter. [ABSTRACT FROM AUTHOR]

This paper describes a simplified analytical solution for computing the magnitude and the point of application of the resultant passive earth thrust, as well as the passive earth pressure distribution against inclined walls retaining unsaturated soils under different steady flow conditions. The present analysis was performed based on the assumptions consistent with the Coulomb approach within the framework of the limit equilibrium method. Possible modifications of induced negative pore pressure or matric suction within the unsaturated zone above the water table have been considered depending upon the steady flow conditions, soil types, and groundwater table positions. Results of the parametric study showed considerable alterations in the passive earth pressure of unsaturated soils due to different parameters and highlight the importance of incorporating suction stress changes directly in the stability analysis of earth-retaining structures. [ABSTRACT FROM AUTHOR]

This work theoretically analyzed the role played by intrinsic degrees of freedom of the colliding partners and/or nucleon transfer channel in the fusion dynamics of 1 2 C + 9 2 Zr and 1 2 C + 1 9 4 , 1 9 8 Pt reactions. The theoretical calculations for the chosen reactions have been done by using symmetric–asymmetric Gaussian barrier distribution (SAGBD) model, coupled channel code CCFULL and one-dimensional Wong formula. The fusion excitation functions for these reactions are enhanced at energies lying in the sub-barrier regions with respect to calculations based on one-dimensional Wong formula. Such enhancement can be ascribed to the involvement of the low-lying inelastic surface excitations of the colliding systems and some other favored channels. The CCFULL calculations consider the couplings to low lying vibrational states of target isotopes and hence intimate the dominance of the collective excitations associated with the fusing partners. For all the studied reactions, the SAGBD model adequately addresses the sub-barrier fusion dynamics and thus the impacts of nuclear structure degrees of freedom associated with the collision partners are intrinsically incorporated via single Gaussian type of weight function. In the SAGBD approach, the nuclear structure effects are analyzed in terms of channel coupling parameter (λ) and percentage reduction of effective fusion barrier V CBRED with reference to the Coulomb barrier. The larger values for λ and V CBRED imply that the channel couplings due to internal structure of participants are significant at below barrier energies. The CCFULL calculations and SAGBD predictions consistently explain the fusion dynamics of chosen systems and hence reveal that both models have almost similar predictive power with respect to reported fusion data. [ABSTRACT FROM AUTHOR]

The fusion process is the effect of a one-dimensional barrier penetration model that incorporates scattering potential as a combination of Coulomb and proximity potentials. Heavy-ion fusion reactions were performed with coupled-channel (CC) calculations. In heavy-ion fusion reactions, CC formalism is carried through the under-barrier energy. Here, fusion cross sections were calculated and investigated for the O16+Ge70;72;74;76, O16+Sm148;150;152;154, Ne20+Zr90;92;94;96, Ne20+Sn112;114;116;118;120, Si28+ Mo90;96, Si28+Mg24;26, Si28+Ni58;64, Si28+Zr90;94;96, S32+Zr90;96, S36+ Pb204;206;208;210, Ar40+Hf176;178;180 in the framework of CC calculations (CCFULL, NRV) and Wong's formula. Fusion cross sections were analyzed in detail by CC calculations considering 2+ and 3- excitation modes for the projectile and the target. The calculated cross-section results were compared with the experimental data. The calculations were found to produce reliable data compared to experimental data. Fusion barrier distributions (Dfus) for all reactions have been investigated below and above the Coulomb barrier using the coupled-channel method with CCFULL, NRV codes and second derivative of Wong's formula. The harmony among these calculations was examined and it was determined that the models were in harmony with each other. [ABSTRACT FROM AUTHOR]

In the current work the calculations of the reaction cross-section of total fusion Dfus, the fusion barrier distribution Dfus, and the semiclassical and quantum mechanics treatments comprise the approximation of WKB for describing the relative motion among projectile nuclei and target nuclei, and the method of CDCC (Continuum Discretized Coupled Channel) for describing the intrinsic motion for the projectile and target nuclei. Our semiclassical calculations yielded findings that were compared to obtainable experimental data as well as quantum mechanics calculations. For fusion cross-sections fus below and above the Coulomb barrier Vb, the quantum mechanics coupled channels are very similar, very similar, according to the experimental results. [ABSTRACT FROM AUTHOR]

We show that the application of a vertical electric field to the Coulomb interacting system in stacked quantum dots leads to a 90° in-plane switching of charge probability distribution in contrast to a single dot, where no such switching exists. Results are obtained using path integral quantum Monte Carlo with realistic dot geometry, alloy composition, and piezo-electric potential profiles. The origin of the switching lies in the strain interactions between the stacked dots hence the need for more than one layer of dots. The lateral polarization and electric field dependence of the radiative lifetimes of the excitonic switch are also discussed. [ABSTRACT FROM AUTHOR]

Prussian blue analogues magnetic nanoparticles (of radius R0=2.4-8.6 nm) embedded in PVP (polyvinylpyrrolidone) or CTA+ (cetyltrimethylammonium) matrices have been studied using neutron diffraction and small angle neutron scattering (SANS) at several concentrations. For the most diluted particles in neutral PVP, the SANS signal is fully accounted for by a "single-particle" spherical form factor with no structural correlations between the nanoparticles and with radii comparable to those inferred from neutron diffraction. For higher concentration in PVP, structural correlations modify the SANS signal with the appearance of a structure factor peak, which is described using an effective "mean-field" model. A new length scale R*≈3R0, corresponding to an effective repulsive interaction radius, is evidenced in PVP samples. In CTA+, electrostatic interactions play a crucial role and lead to a dense layer of CTA+ around the nanoparticles, which considerably alter the SANS patterns as compared to PVP. The SANS data of nanoparticles in CTA+ are best described by a core-shell model without visible inter-particle structure factor. [ABSTRACT FROM AUTHOR]

Until now, the technique was thought to work only on molecules with no more than about five atoms. A powerful x-ray source leaves that limit in the dust. [ABSTRACT FROM AUTHOR]

The study of fusion reactions at extreme sub-barrier energies has seen an increased interest in recent years, although difficult to measure due to their very small cross sections. Such reactions are extremely important for our understanding of the production of heavy elements in various environments. In this article, the status of the field is reviewed covering the experimental techniques, the available data, and the theoretical approaches used to describe such reactions. The fusion hindrance effect, first discovered in medium-mass systems, has been found to be relevant also for lighter systems. In some light systems, resonance structures are found to be important, while for heavy systems, the fission process plays an important role. In the near barrier region, couplings to collective excitations in the fusion participants and transfer reactions have been found to give a good description of the measured fusion cross sections and it results in a distribution of fusion barrier heights. New physics ingredients, related to the overlap process of the two projectiles, have to be introduced to describe the hindrance behavior. In addition, it has recently been found that the fusion cross section in both near-barrier and sub-barrier regions can be described very well in many cases using simple, analytical forms of the barrier-height distributions or a modified version of the classic Wong formula. [ABSTRACT FROM AUTHOR]

Experimental fission cross-sections are reported for the 19F + 194,196,198Pt reactions populating an isotopic chain of compound nuclei comprising both closed and non-closed shell nuclei. The fission cross-sections are obtained at near and above Coulomb barrier energies by measuring fission fragment angular distributions. The present work aims to estimate nuclear dissipation and find its isotopic and shell closure dependence from statistical model (SM) analysis of experimental data. Pre-scission neutron multiplicity data for the same systems is also included in the SM analysis. An updated version of SM is used in the present analysis, which includes shell corrections in level density and fission barrier as well as the effect of collective enhancement of level density and orientation effect of the compound nucleus along the symmetry axis. An isotopic dependence of the dissipation strength fitting the fission excitation functions is observed. The pre-scission neutron multiplicity, however, is underestimated by the SM. [ABSTRACT FROM AUTHOR]

The present paper examines the effect of temperature-dependent repulsive core potential on the fusion reactions of the α particle relevant to the production of p-nuclei such as 154 Sm, 162 Dy, 166 Er, and 197 Au. For this purpose, the α -nucleus potentials making use of the double folding model with the density-dependent CDM3Y3 interaction plus the temperature-dependent repulsion (CDM3Y3+Repulsion) are employed. In addition, three nuclear level density (NLD) models of Fermi-Gas (FG), Hartree–Fock BCS (HFBCS), and exact pairing plus independent-particle model (EP+IPM) are used to describe the temperature-dependent excitation energy of the compound nucleus produced in the fusion reaction. The results obtained show that temperature has a significant effect on the repulsive core potential, and different NLD models predict different fusion potentials, especially at high temperatures and near the center point (origin) of the interaction. Going further away from the origin, the repulsive core potential decreases to approximately zero near the barrier region, while at sufficiently far distances, it is least affected by nuclear temperature. The calculated fusion cross sections using the CDM3Y3+Repulsion potential are only affected by the diffuseness parameter of the repulsive potential a rep. in the region above the Coulomb barrier, and a good agreement with the experimental data is found at a rep. = 0.35 fm. Hence, the effect of repulsive potential on the α -induced reactions is only justified as a correction term, which is added to resolve the Pauli principle problem. This conclusion is in line with those reported previously using similar formalism but for other fusion reactions of heavy nuclei. [ABSTRACT FROM AUTHOR]

A recent comparison of the average fusion cross section, σ F , for energies just above the Coulomb barrier for the 12 - 15 C + 12 C systems found that the behaviour as a function of projectile neutron excess could not be satisfactorily explained by static barrier penetration model calculations and suggested that the neutron dynamics plays an important rôle. In this work we demonstrate that the ( 15 C, 14 C) single neutron transfer has a significant influence on the above barrier 15 C + 12 C total fusion, although not quite in the way expected since it leads to a reduction in the cross section, contrary to the trend in the measured σ F . However, this result underlines the danger of ignoring the effect of neutron transfer reactions on fusion in systems involving neutron halo nuclei. [ABSTRACT FROM AUTHOR]

Major Atlantic hurricanes Irma, Jose, and Maria of 2017 reached their peak intensity in September while traveling over the tropical North Atlantic Ocean and Caribbean Sea, where both atmospheric and ocean conditions were favorable for intensification. In situ and satellite ocean observations revealed that conditions in these areas exhibited (i) sea surface temperatures above 28°C, (ii) upper-ocean heat content above 60 kJ cm-2, and (iii) the presence of low-salinity barrier layers associated with a larger-than-usual extension of the Amazon and Orinoco riverine plumes. Proof-of-concept coupled ocean--hurricane numerical model experiments demonstrated that the accurate representation of such ocean conditions led to an improvement in the simulated intensity of Hurricane Maria for the 3 days preceding landfall in Puerto Rico, when compared to an experiment without the assimilation of ocean observations. Without the assimilation of ocean observations, upper-ocean thermal conditions were generally colder than observations, resulting in reduced air--sea enthalpy fluxes--enthalpy fluxes are more realistically simulated when the upper-ocean temperature and salinity structure is better represented in the model. Our results further showed that different components of the ocean observing system provide valuable information in support of improved TC simulations, and that assimilation of underwater glider observations alone enabled the largest improvement over the 24 h time frame before landfall. Our results, therefore, indicated that ocean conditions were relevant for more realistically simulating Hurricane Maria's intensity. However, further research based on a comprehensive set of hurricane cases is required to confirm robust improvements to forecast systems. [ABSTRACT FROM AUTHOR]