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Statistical fluctuations of nuclear energy spectra for the isobar A = 68 were examined by means of the random matrix theory together with the nuclear shell model. The isobar A = 68 nuclei are suggested to consist of an inert core of 56Ni with 12 nucleons in f5p-space (2p3/2, 1f5/2 and 2p1/2 orbitals). The nuclear excitation energies, required by this work, were obtained through performing f5p-shell model calculations using the isospin formalism f5pvh interaction with realistic single particle energies. All calculations of the present study were conducted using the OXBASH code. The calculated level densities were found to have a Gaussian shape. The distributions of level spacing P(s) and Δ3 statistic for the considered classes of states, obtained with full Hamiltonian of f5pvh (absence of the off-diagonal Hamiltonian) calculations, showed a chaotic (regular) behavior and coincided well with the distribution of Gaussian orthogonal ensemble (Poisson). Moreover, these distributions were independent of spin ( J ) and isospin (T ). [ABSTRACT FROM AUTHOR]

The temperature and pressure dependence of isobaric thermal expansivity, αp, in liquids is discussed in this paper. Reported literature data allow general trends in this property that are consistent with experimental evidence to be established. Thus, a negative pressure dependence is to be expected except around the critical point. On the other hand, αp exhibits broad regions of negative and positive temperature dependence in the (T, p) plane depending on the nature of the particular liquid. These trends are rationalized here in terms of various molecular-based equations of state. The analysis of the Lennard-Jones, hard sphere square well and restricted primitive model equations allows understanding the differences in the αp behavior between liquids of diverse chemical nature (polar, nonpolar, and ionic): broader regions of negative temperature and positive pressure dependencies are obtained for liquids characterized by larger ranges of the interparticle potential. Also, using the statistical associating fluid theory (SAFT) allowed the behavior of more complex systems (basically, those potentially involving chain and association effects) to be described. The effect of chain length is rather simple: increasing it is apparently equivalent to raise the interaction range. By contrast, association presents a quite complex effect on αp, which comes from a balance between the dispersive and associative parts of the interaction potential. Thus, if SAFT parameters are adjusted to obtain low association ability, αp is affected by each mechanism at clearly separate regions, one at low temperature, due to association, and the other to dispersive forces, which has its origin in fluctuations related with vapor-liquid transition. [ABSTRACT FROM AUTHOR]

We present experimental data of the isobaric heat capacity per unit volume Cp,xV-1 for mixtures containing nitrobenzene and an alkane (CNH2N+2, with N ranging from 6 to 15) upon approaching their liquid-liquid critical points along a path of constant composition. Values for the critical amplitude A+ have been determined. They have been combined with the previously reported ones for the leading term of the coexistence-curve width to obtain, with the aid of well-known universal relations, the critical amplitudes of the correlation length and of the osmotic susceptibility. The trends of all these critical parameters, which exhibit anomalous behavior in the low N region, are discussed in terms of particular microscopic phenomena characterizing NB-CNH2N+2 mixtures. The work is completed with an analysis of the analog of the Yang-Yang anomaly in liquid-liquid criticality: the behavior of the partial molar heat capacities of the two liquid components is found to illustrate previously uncovered asymmetry effects. [ABSTRACT FROM AUTHOR]

The authors present a new molecular dynamics algorithm for sampling the isothermal-isobaric ensemble. In this approach the velocities of all particles and volume degrees of freedom are rescaled by a properly chosen random factor. The technical aspects concerning the derivation of the integration scheme and the conservation laws are discussed in detail. The efficiency of the barostat is examined in Lennard-Jones solid and liquid near the triple point and compared to the deterministic Nosé–Hoover and the stochastic Langevin methods. In particular, the dependence of the sampling efficiency on the choice of the thermostat and barostat relaxation times is systematically analyzed. [ABSTRACT FROM AUTHOR]

Abstract Routine measurements of the last years at the 6 MV AMS system showed a good isobar suppression for all light isotopes, measured with the Degrader-Foil-Method, especially 36Cl and 10Be. However, the efficiency is reduced due to the charge state distribution generated by the degrader-foil. For measurements injecting atomic 26Al, the ionization efficiency becomes the bottleneck, which leads to a relatively low ion source output. In the case of AlO−, the output is expected about one order of magnitude higher. However, to use AlO− the isobar interference of 26Mg will become an issue. It has to be suppressed in several steps, e.g. by different dE/dx methods like TOF, degrader-foil or gas-filled magnet. In order to minimize the efficiency losses generated by the degrader-foil method, the 120°-magnet at the 6 MV AMS system was modified to enable a gas-filled operation, and therefore focus the beam to a mean charge state. A constraint for all modification of the detection beam line was that the operation of the degrader-foil method is not affected. In this paper, we report on the performed construction work, as well as test measurements for 27Al at 40 MeV ion energy. Isobar separation for 36Cl and 36S was measured as a function of the gas pressure. We compare measured data with Monte Carlo simulations performed with a computer code developed by our group. In addition, we will present a new dedicated gas ionization chamber designed for particle detection directly after the gas-filled magnet. [ABSTRACT FROM AUTHOR]

Abstract Three applications based on the passage of channeled ions through a crystalline membrane are proposed for the accelerator mass spectrometry (AMS) technology. (i) A channeling degrader for the separation of isobars suppresses the angular straggling even if a sufficient energy difference is created between the AMS nuclide and its isobars using a relatively thick membrane. A proof-of-principle experiment showed its potential comparative advantage. Feasibility will be discussed for two other potential applications; the experimental demonstrations are under consideration. (ii) A channeling stripper simultaneously provides a sufficient stripping function to remove interfering molecules in the AMS and low gas pressure to prevent ion scattering. This helps in overcoming a crucial problem in the development of an (A)MS systems in the range of 50 keV. Surface channeling by grazing incidence onto a stack of mono-crystalline substrates is introduced to address the high particle load. (iii) A novel isobar separation technique, using resonant coherent excitation based on periodical field induced by ions passing through the lattice, assists in controlling the charge state of the AMS nuclide and its isobars directly. For practical use, the thickness of the crystalline membrane should be reduced to satisfy the charge state distribution in the non-equilibrium states. [ABSTRACT FROM AUTHOR]

The Δ-isobar degrees of freedom are included in the covariant density functional (CDF) theory to study the equation of state (EoS) and composition of dense matter in compact stars. In addition to Δ's we include the full octet of baryons, which allows us to study the interplay between the onset of delta isobars and hyperonic degrees of freedom. Using both the Hartree and Hartree–Fock approximation we find that Δ's appear already at densities slightly above the saturation density of nuclear matter for a wide range of the meson–Δ coupling constants. This delays the appearance of hyperons and significantly affects the gross properties of compact stars. Specifically, Δ's soften the EoS at low densities but stiffen it at high densities. This softening reduces the radius of a canonical 1.4 M ⊙ star by up to 2 km for a reasonably attractive Δ potential in matter, while the stiffening results in larger maximum masses of compact stars. We conclude that the hypernuclear CDF parametrizations that satisfy the 2 M ⊙ maximum mass constraint remain valid when Δ isobars are included, with the important consequence that the resulting stellar radii are shifted toward lower values, which is in agreement with the analysis of neutron star radii. [ABSTRACT FROM AUTHOR]

We present an analysis of the spectator mechanism of Δ-isobar production in the pion photoproduction on nuclei with the emission of two nucleons. The reaction mechanism is studied within the framework of the ΔN-correlation model, which considers the isobar and nucleon of the ΔN-system produced in the nucleus at the virtual NN→ΔN transition to be in a dynamic relationship. The two-particle transition operator for nuclei is obtained by the S-matrix approach. We consider the properties of the spectator mechanism of isobar production using the example of the reaction 16O(γ,π−pn)14O. Numerical estimates of the cross-section are obtained in the kinematic region, where it is possible to expect the manifestation of bound isobar-nuclear states. [ABSTRACT FROM AUTHOR]

The estimation of spectroscopic properties of neutron-deficient nuclei in the A=100 tin mass region is needed for the understanding of the rp-process path and the experimental exploration of the nuclear landscape. In order to evaluate some spectroscopic properties of the Gamow-Teller b+ decay of neutron deficient isobars of A = 100, we have performed shell model calculations by means of Oxbash nuclear structure code. The jj45pn valence space used consists of nine proton and neutron orbitals. The calculations included few valence hole-proton and particle-neutronin πg9/2 and vg7/2 orbitals respectively, in 100Sn doubly magic core. Effective interaction deduced from CD-Bonn one is introduced taking into account the nuclear monopole effect in this mass region. The results are then compared with the available experimental data. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry (SIMS) provides spatially resolved trace analysis of solid materials, but can be complicated by unresolved abundant molecular isobars. By adding a 300-kV single-stage accelerator mass spectrometer (SSAMS) as a detector for a Cameca ims 4f SIMS, one can measure more abundant positive ions from the SIMS while removing molecular isobars, thus improving very low abundance trace element and isotope analysis. This paper describes important features and capabilities of such an integrated system at the Naval Research Laboratory using charge state +1 ions. Transmission loss is compared to molecule destruction as gas flow to the molecule-destruction cell increases. As most measurements tolerate more modest abundance sensitivities than for 14 C analysis, a lower gas flow is acceptable, so good transmission of 20–50% for ions of interest can be maintained for a broad range of ion masses. This new instrument has measured isotope ratios for uranium, lead, rare earths, and other elements from particulates and localized regions, with molecule destruction enabling the measurement at low SIMS mass resolving power and thus high transmission, as examples will show. This new and world-unique instrument provides improved capabilities for applications in nuclear and other forensics, geochemistry, cosmochemistry, and the development of optical, electronic, multifunctional, and structural materials. [ABSTRACT FROM AUTHOR]

We present a novel method for rapid and high-sensitivity in situ measurements of the rare earth elements (REEs) by combined secondary ion mass spectrometry and single-stage accelerator mass spectrometry (SIMS-SSAMS). Traditional SIMS can be limited in its REE sensitivity by the presence of abundant molecular isobars, whose discrimination is often beyond the range of high mass resolving power, and which require energy filtering and careful calibration to deconvolve. These greatly reduce sensitivity and require a priori assumption of terrestrial isotope ratios for deconvolution, which precludes the analysis of some nuclear forensic materials and presolar stardust grains. With the SSAMS, molecular background is reduced by 5 to 6 orders of magnitude, precluding the need for energy filtering and/or high mass resolution. We demonstrate measurement of Gd isotopes (6 μmol mol−1) in the presence of a molecular background more than 4 orders of magnitude more intense from a single 15 μm spot in a sample of Madagascar hibonite. From the same spot we can resolve 7 nmol mol−1 of Tm from its comparably large background. Traditional SIMS requires the measurement of 47+ masses over 0.5 to 3 hours to perform REE deconvolution, while we collect full REE abundance patterns from several minerals in 10 to 30 minutes per spot. We observe no instrumental mass fractionation (±1%) in either Gd or Dy isotope ratio measurements of NIST610/612 glass. These improvements in sensitivity and measurement rapidity open important new avenues for REE imaging of samples and analyses of particles, nuclear materials, and mineral inclusions. [ABSTRACT FROM AUTHOR]

The evaluators present in this publication spectroscopic data and level schemes from radioactive decay and nuclear reactions studies for all isobars with mass number A = 99 . [ABSTRACT FROM AUTHOR]

The recoil-catcher activation technique followed by the offline γ -ray spectroscopy has been adopted for the excitation function measurement of residues populated in 12,13 C induced reactions with 175 Lu target at lower projectile energies ≈ 4 – 8 MeV / nucleon . The independent cross-sections for some of the populated residues have been estimated by subtracting the contributions of higher charge precursor isobars from the measured cumulative cross-sections. The measured excitation functions are compared with theoretical predictions based on statistical model code PACE-4. This comparison reveals that complete fusion process solely contributes in the formation of xn-pxn channels and an enhancement in the measured cross-sections of α -emitting channels from the theoretical predictions may be attributed to the incomplete fusion process. The incomplete fusion probability is found to be higher in case of C 12 than for a one neutron rich projectile C 13 throughout the incident energy region. Present findings obtained for 12,13 C + 175 Lu systems have been compared with informations extracted from previously studied systems and projectile structure is found to strongly affect the incomplete fusion dynamics in terms of projectile α - Q -value along with projectile-target mass-asymmetry. Moreover, it may be pointed out that Morgenstern's mass-asymmetry systematic is probably the projectile structure dependent systematic. A substantial contribution to incomplete fusion coming from collision trajectories with ℓ ≤ ℓ crit is also observed, contrary to the SUMRULE model assumptions. [ABSTRACT FROM AUTHOR]

The phenomenon of signature inversion observed in the $\pi h_{11/2} \otimes\nu i_{13/2}$ band of Eu and Tb nuclides is revisited through the axially symmetric two quasiparticle plus rotor model approach. The magnitude of experimentally observed signature splitting and point of signature inversion, which could not be explicitly reproduced in the earlier calculations, is successfully reproduced in the present study. Some of the critical issues, such as violation of the well-established Gallagher Moszkowski (GM) rule for eight GM doublets appearing in the basis space of earlier calculations of Eu and Tb , are fixed and also the ambiguity regarding spin assignment to this band observed in Tb is resolved. These calculations are further extended to the same band ( $\pi h_{11/2} \otimes\nu i_{13/2}$ ) observed in Tb nuclide and signature inversion observed in this band is successfully reproduced. [ABSTRACT FROM AUTHOR]

The level structures of 70 Co and 70 Ni, populated from the β decay of 70 Fe, have been investigated using β -delayed γ -ray spectroscopy following in-flight fission of a 238 U beam. The experimental results are compared to Monte-Carlo Shell-Model calculations including the p f + g 9 / 2 + d 5 / 2 orbitals. The strong population of a ( 1 + ) state at 274 keV in 70 Co is at variance with the expected excitation energy of ∼1 MeV from near spherical single-particle estimates. This observation indicates a dominance of prolate-deformed intruder configurations in the low-lying levels, which coexist with the normal near spherical states. It is shown that the β decay of the neutron-rich A = 70 isobars from the new island of inversion to the Z = 28 closed-shell regime progresses in accordance with a newly reported type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps. [ABSTRACT FROM AUTHOR]

The Fuente de Piedra lake is a hypersaline wetland of great extension (13.5 km 2 ) and rich in aquatic birds and other species. It became therefore the third Spanish wetland to be included in the Ramsar convention and has been a “nature reserve” since 1984. The lake has an endorheic basin (150 km 2 ) with variable-density flows dominated by complex hydrogeological conditions. The traditional conceptualization of endorheic basins in semiarid climates considered that the brine in this hydric system was exclusively of evaporative origin and was placed only in the lake and its surrounding discharge area in the basin. Previous geophysical and hydrochemical studies identified different types of waters and brines. In this work, natural tracers (Cl − , Br − , Na + , Mg 2+ ) and environmental isotopes ( 18 O, 2 H, 14 C, 13 C and 3 H) were employed to a) discriminate different types of brines according to their degree of evaporation and genesis, and b) to estimate residence times of brine waters and identify recharge areas of the different flow subsystems. A conceptual model of the hydrogeological system of the lake basin and its links to a regional karst system is proposed. [ABSTRACT FROM AUTHOR]

A heavy-ion detector was developed for decay studies in the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. This detector serves as a prototype for the in-pocket particle detectors for future experiments with the Collector Ring (CR) at FAIR (Facility for Antiproton and Ion Research). The detector includes a stack of six silicon pad sensors, a double-sided silicon strip detector (DSSD), and a CsI(Tl) scintillation detector. It was used successfully in a recent experiment for the detection of the β + -decay of highly charged 142 Pm 60+ ions. Based on the Δ E / E technique for particle identification and an energy resolution of 0.9% for Δ E and 0.5% for E (Full Width at Half Maximum (FWHM)), the detector is well-suited to distinguish neighbouring isobars in the region of interest. [ABSTRACT FROM AUTHOR]

The isotopic structure of the well-established s-wave resonances in the presence of a hypnotized narrow resonance N(1670)1/2 in the amplitude is discussed. Two sets of results coming out of fitting two different sets of the data are discussed. [ABSTRACT FROM AUTHOR]

The effect of BWR fuel assembly 3D model on void reactivity coefficient (VRC) estimation is investigated. VRC values were calculated for different BWR assembly models applying deterministic T-NEWT and Monte Carlo KENO-VI functional modules of SCALE 6.1 code package. The difference between deterministic T-NEWT and Monte Carlo KENO-VI simulations is negligible (0.18 pcm/%). The influence of the assumed more detailed coolant density profile was estimated as well. VRC increases with the application of a larger number of coolant density values across fuel assembly height. It was shown that the coolant density profile described by 6 values per height could be considered sufficient from prospect of VRC estimation, as a more detailed density profile has impact below 1% on total assembly void effects. VRC values were decomposed to values for individual nodes and isotopes, since decomposition provides useful insights to describe the overall behaviour of VRC in detail. [ABSTRACT FROM AUTHOR]

The results based on the spectroscopy of superheavy hydrogen isotopes (H), heavy helium isotopes (He), and heavy lithium isotopes (Li) produced in stopped pion absorption by light nuclei were analyzed. Search for nuclear states was performed in inclusive and correlation measurements of missing mass spectra. A broad range of excitation energies studied in correlation measurements provided the possibility of search for isobaric analog states and cluster resonances. A comparison with experimental and theoretical results of other authors was conducted. [ABSTRACT FROM AUTHOR]

On the basis of the shell model with an extended basis, the structure of Li-Be to Li-Be nuclei is examined with allowance for the competition of coupling and Majorana exchange forces via considering the sequential addition of neutrons, and the respective wave functions are determined. A formalism for calculating the spectroscopic factor for a dineutron and for individual neutrons in nuclei whose wave functions incorporate the mixing of shell configurations is developed. The reactions Li( t, p)Li and Be( t, p)Be treated with allowance for the mechanisms of dineutron stripping and a sequential transfer of two neutrons are considered as an indicator of the proposed structure of lithium and berylliumisotopes. The parameters of the optical potentials, the wave functions for the bound states of transferred particles, and the interaction potentials corresponding to them are determined from a comparison of the theoretical angular distribution of protons from the reaction Be( t, p)Be with its experimental counterpart. It is shown that a dineutron periphery of size about 6.4 fm is present in the Li nucleus and that a single-neutron periphery of size about 8 fm is present in the Be nucleus. [ABSTRACT FROM AUTHOR]

The 2015 update of the discovery of nuclide project is presented. Twenty new nuclides were observed for the first time in 2015. An overall review of all previous assignments was made in order to apply the discovery criteria consistently to all elements. In addition, a list of isotopes published so far only in conference proceedings or internal reports is included. [ABSTRACT FROM AUTHOR]

93 Zr ( t 1/2 = 1.6 Ma) is mostly produced by the main s -process in low-to-intermediate mass AGB stars. Large uncertainty exists in the current 92 Zr(n,γ) 93 Zr Maxwellian Average cross section. This could have significant impact on nucleosynthesis calculations. Large amounts of 93 Zr are also produced in nuclear reactors and pose long-term environmental radioactivity. Hence, measurement of 93 Zr by the AMS is important for both fields above. We report here on progress in the development of AMS method to measure 93 Zr. Compared with 98 MeV beam energy, Zr/Nb isobar position separation was improved using 155.2 MeV beam energy and Gas-Filled Magnet. Energy loss measurement with increased beam energy inside the detector indicates that higher beam energy can improve isobar energy loss separation. A chemical procedure to reduce the Nb content in Zr samples has been developed and tested. It reduces the 93 Nb content by a factor of 1000. [ABSTRACT FROM AUTHOR]

Background: Triplet energy differences (TED) can be studied to yield information on isospin-non-conserving interactions in nuclei. Purpose: The systematic behavior of triplet energy differences (TED) of T=1, Jπ=2+ states is examined. The A=62 isobar is identified as having a TED value that deviates significantly from an otherwise very consistent trend. This deviation can be attributed to the tentative assignments of the pertinent states in 62Ga and 62Ge. Methods: An in-beam γ-ray spectroscopy experiment was performed to identify excited states in 62Ga using Gamma-Ray Energy Tracking In-Beam Nuclear Array with the S800 spectrometer at NSCL using a two-nucleon knockout approach. Cross-section calculations for the knockout process and shell-model calculations have been performed to interpret the population and decay properties observed. Results: Using the systematics as a guide, a candidate for the transition from the T=1, 2+ state is identified. However, previous work has identified similar states with different Jπ assignments. Cross-section calculations indicate that the relevant T=1, 2+ state should be one of the states directly populated in this reaction. Conclusions: As spins and parities were not measurable, it is concluded that an unambiguous identification of the first T=1, 2+ state is required to reconcile our understanding of TED systematics [ABSTRACT FROM AUTHOR]

The nucleon-nucleon interaction arising from the exchange of three pions and the excitation of Δ(1232) isobars in intermediate states is studied. Approximating the Δ propagator by the inverse ΔN mass-splitting, analytical expressions are derived for the spectral functions of the isoscalar and isovector central, spin-spin, and tensor NN potentials in momentum-space. A translation of the spectral functions into coordinate-space potentials reveals that the main effect of these specific exchange and excitation mechanisms is a repulsive isoscalar central NN potential [ABSTRACT FROM AUTHOR]

In this work, the role of the Δ* resonances in the process of pp → nK+Σ+ are systematically investigated with the effective Lagrangian approach and the isobar model. We find that a P31 state, either Δ*(1750) or Δ*(1910) is favored by the data while the P33 state, namely Δ*(1920), has small contribution. Besides, either the subthreshold S31Δ*(1620) resonance or strong nΣ final state interaction or both have a possible contribution at near threshold region, depending on the measured cross sections. We demonstrate the invariant mass distributions and the Dalitz plots in order to investigate whether it is possible to distinguish the controversial KΣ production mechanism in these observables. [ABSTRACT FROM AUTHOR]

We present a comparative analysis of two models for the A ( γ , π N ) B reaction, which take into account the isobar configurations in the ground state of the nuclei: the Δ N correlation model and the quasifree pion photoproduction model. The considered models differ in their descriptions of the nucleus states. The Δ N correlation model takes into account the dynamic correlations of the nucleon and isobar formed in the virtual transition N N → Δ N , and in the quasifree pion photoproduction model, isobars and nucleons in the nucleus are considered as independent constituents. The predictions of the models are considered for two reactions O 16 ( γ , π + p ) C 15 and O 16 ( γ , π − p ) O 15 . It is shown, that the two models predict the differential cross section significantly differing both in absolute values, and in the shape of the angular dependence. We compare the results of the Δ N correlation model for the ( γ , π N ) and ( γ , π N N ) reactions with the O 16 ( γ , π − p ) reaction data measured at BNL. Our results give support to the Δ N correlation model. [ABSTRACT FROM AUTHOR]

Differential cross sections of the exclusive process ep -> e'π+n were measured with good precision in the range of the π+n photon virtuality Q²=1.8-4.5 GeV², and the invariant mass range of the final state W=1.6-2.0 GeV using the CEBAF Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the np+ center-of-mass system. More than 37,000 cross section points were measured. The contributions of the isospin I=1/2 resonances N(1675)5-/2, N(1680)5+/2 and N(1710)1+/2 were extracted at different values of Q² using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed-t dispersion relations, were employed in the analysis. We observe significant strength of the N(1675)5-/2 in the A1/2 amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the N(1680)5+/2 we observe a slow changeover from the dominance of the A3/2 amplitude at the real photon point (Q²=0) to a Q² where A1/2 begins to dominate. The scalar amplitude S1/2 drops rapidly with Q2 consistent with quark model prediction. For the N(1710)1+/2 resonance our analysis shows significant strength for the A1/2 amplitude at Q²<2.5 GeV². [ABSTRACT FROM AUTHOR]