Spin Assignments Research Articles

Spins and magnetic moments ofMn58,60,62,64ground states and isomers

The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39 were extracted. The previous tentative ground state spin assignments of 58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4 assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments show a decreasing trend with increasing neutron number while the I = 4 moments remain quite constant between N = 33 and N = 37. The results are compared to large-scale shell-model calculations using the GXPF1A and LNPS effective interactions. The excellent agreement of the ground state moments with the predictions from the LNPS calculations illustrates the need for an increasing amount of proton excitations across Z = 28 and neutron excitations across N = 40 in the ground state wave functions from N = 37 onwards.

Nuclear structure of 37, 38Si investigated by decay spectroscopy of 37, 38Al

We present a study on the β decays of the neutron-rich isotopes 37Al and 38Al, produced by projectile fragmentation of a 48Ca beam with an energy E = 345 A MeV at the RIKEN Nishina Center. The half-lives of 37Al and 38Al have been measured to 11.5(4)ms and 9.0(7)ms, respectively, using the CAITEN implantation and decay detector setup. The level schemes for 37Si and 38Si were deduced by employing γ-γ coincidence spectroscopy following the event-by-event identification of the implanted nuclei. Comparison to large scale nuclear shell model calculations allowed for a tentative assignment of spin and parity of the populated states. The data indicate that the classical shell gap at magic neutron number N = 28 between the νf7/2 and νp3/2 orbits gets reduced by 0.3 MeV in this region leading to low-energy states with intruder configuration in 37Si.

Predicting superdeformed rotational band-head spin in A ∼ 190 mass region using variable moment of inertia model

The band-head spin (I 0) of superdeformed (SD) rotational bands in A∼190 mass region is predicted using the variable moment of inertia (VMI) model for 66 SD rotational bands. The superdeformed rotational bands exhibited considerably good rotational property and rigid behaviour. The transition energies were dependent on the prescribed band-head spins. The ratio of transition energies over spin E γ/2I (RTEOS) vs. angular momentum (I) have confirmed the rigid behaviour, provided the band-head spin value is assigned correctly. There is a good agreement between the calculated and the observed transition energies. This method gives a very comprehensive interpretation for spin assignment of SD rotational bands which could help in designing future experiments for SD bands.

Measurement of theMo97(n,γ)reaction with the DANCEγcalorimeter array

Spectra of $\ensuremath{\gamma}$ rays following the $^{97}\mathrm{Mo}(n,\ensuremath{\gamma})$ reaction were measured as a function of incident neutron energy with the DANCE (Detector for Advanced Neutron Capture Experiments) array of $160 {\mathrm{BaF}}_{2}$ scintillation detectors at the Los Alamos Neutron Science Center using an enriched $^{97}\mathrm{Mo}$ target. These spectra were used for the assignment of spins of the $^{97}\mathrm{Mo}$ resonances up to neutron energy ${E}_{n}=1.7$ keV, as well as in the study of photon strength functions (PSFs) in $^{98}\mathrm{Mo}$. Analysis of the spectra with the nuclear statistical model showed that they can be well reproduced with the same PSF models which well described the $\ensuremath{\gamma}$ decay following slow neutron capture in $^{95}\mathrm{Mo}$. On the other hand, the spectra are inconsistent with PSFs describing some other experimental data in $^{98}\mathrm{Mo}$.

Structure of 207Pb populated in 208Pb + 208Pb deep-inelastic collisions

The yrast structure of 207Pb above the 13=2+ isomeric state has been investigated in deep-inelastic collisions of 208Pb and 208Pb at ATLAS, Argonne National Laboratory. New and previously observed transitions were measured using the Gammasphere detector array. The level scheme of 207Pb is presented up to ∼ 6 MeV, built using coincidence and γ-ray intensity analyses. Spin and parity assignments of states were made, based on angular distributions and comparisons to shell model calculations.

Nuclear Data Sheets for A = 247

Available information pertaining to the nuclear structure of all nuclei with mass numbers A=247 is presented. Various decay and reaction data are evaluated and compared. Adopted data, levels, spin, parity and configuration assignments are given. When there are insufficient data, expected values from systematics of nuclear properties or/and theoretical calculations are quoted. Unexpected or discrepant experimental results are also noted. A summary and compilation of the discovery of various isotopes in this mass region is given in 2013Fr02 (247Pu, 247Am, 247Cm, 243Bk, 247Cf), 2011Me01 (247Es), and 2013Th02 (247Fm, 247Md).

Study of theΛc+spin at aτ-charm factory

A large cross section for e(+) e(-) -> Lambda(+)(c) (Lambda) over bar (-)(c) pair production near its threshold provides an opportunity to study the charm baryon Lambda(+)(c) (Lambda) over bar (-)(c) at a tau-charm factory with e(+) e(-) collisions. We call for the determination of the Lambda(+)(c) (Lambda) over bar (-)(c) spin using the process e(+) e(-) -> Lambda(+)(c) (Lambda) over bar (-)(c), Lambda(+)(c) -> pK(s)(0), and we present a formula and a method to estimate the statistical significance for spin assignment J = 1/2 and J = 3/2. A Monte Carlo study shows that the significance is sensitive to the number of observed events. A few hundred observed signal events will yield the statistical significance larger than five standard deviations.

Structure of $^{207}$Pb Populated in $^{208}$Pb + $^{208}$Pb Deep-inelastic Collisions

The yrast structure of 207Pb above the 13/2+ isomeric state has been investigated in deep-inelastic collisions of 208Pb and 208Pb at ATLAS, Argonne National Laboratory. New and previously observed transitions were measured using the Gammasphere detector array. The level scheme of 207Pb is presented up to ~ 6 MeV, built using coincidence and γ-ray intensity analyses. In addition, the spin and parity assignments of states were made, based on angular distributions and comparisons to shell model calculations.

“No-spin” states and low-lying structures in130Xe and136Xe

Inelastic neutron scattering on solid 130 XeF 2 and 136 XeF 2 targets was utilized to populate excited levels in 130 Xe and 136 Xe. When calculating nuclear matrix elements vital to the understanding of double-beta decay, it is important to have a clear understanding of the low-lying level structure of both the parent and daughter nucleus. Of particular relevance to double-beta decay searches are the assignments of 0 + states. We show here that in the case of 130 Xe there are several discrepancies in the adopted level structure. We found that one previous 0 + candidate level (1590 keV) can be ruled out and assigned two additional candidates (2223 and 2242 keV). In 136 Xe we question the previous assignment of a 0 + level at 2582 keV. Excitation function and angular distribution measurements were utilized to make spin and parity assignments of levels and place new transitions.

Scissors Mode of162Dy Studied from Resonance Neutron Capture

Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.

Theoretical Determination of Level Spins of Superdeformed Bands for Nuclei in the Mass Region A = 80 – 104

The bandhead spins of seventeen superdefomed bands in A = 80 – 104 region (38Sr, 39Y, 40Zr, 41Nb,42Mo, 43Tc, 46Pd) have assigned by an indirect method. The dynamical moment of inertia J(2) as a function of rotational frequency ђω are extracted from Harris expansion and fitted to the experimental values by using a computer simulated search program. The calculated dynamic moment of inertia with the best optimized parameters are integrated to give the spins. The intrinsic aligned angular momentum (the integration constant) is assumed to be zero. The values of the spins resulting from our approach are consistent with all spin assignments of other approaches, and have been used to determine the kinematic moment of inertia J(1). The systematic variation of J (2) and J (1) with rotational frequency ђω is investigated, which turns out to be helpful in the spin prediction. Most SD bands in this mass region exhibits decreasing in J(1) and J(2) with increasing ђω. The bandhead moment of inertia J0 which occur at J(2) = J (1) has been sensitive guideline parameter to spin proposition. The relationship between the Harris expansion three parameter model and the four parameter Bohr-Mottelson formula is derived.

Validating resonance properties using nuclear resonance fluorescence

Measurement of a resonance's integrated cross section using nuclear resonance fluorescence can be a valuable tool for verifying the properties of the resonance because of the clear and unambiguous physical connection to the spin, lifetime, and ground state branching ratio of the level. We demonstrate this idea by measuring the integrated cross section of the 3.004-MeV level in $^{27}\mathrm{Al}$ to 4% using the monoenergetic $\ensuremath{\gamma}$-ray beam at the High Intensity $\ensuremath{\gamma}$-ray Source. That level was the subject of much debate experimentally in the 1960s, especially its spin, and even now only has a current tentative spin assignment of $J=(9/2)$. The consistency check between this integrated cross section and the known properties of the level indicate that one (or more) of the literature properties is incorrect. Based on the range of extent of each property, a reassignment of spin to a tentative $J=(7/2)$ may be warranted, but this would need to be confirmed with other measurements. This result demonstrates the utility of NRF as a way to verify the properties of states in the literature before undertaking more extensive measurements.

Effect of the reduced pairing interaction onα-decay half-lives of multi-quasiparticle isomeric states

The role of the pairing interaction in multi-quasiparticle isomeric states was examined by calculating $\ensuremath{\alpha}$-decay half-lives with the superfluid tunneling model. We found that this model reproduces the experimental $\ensuremath{\alpha}$-decay half-lives with an accuracy typical of current $\ensuremath{\alpha}$-decay models. In spite of the simplicity of the model, we are able to demonstrate how the reduction of pairing in multi-quasiparticle isomers has a remarkable effect on $\ensuremath{\alpha}$-decay half-lives. Taking this effect into account may be important for spin and parity assignments of $\ensuremath{\alpha}$-decaying multi-quasiparticle isomers.

Revised level structure ofTe120

The level scheme of the nucleus Te-120, populated in the reaction Se-80(Ca-48, alpha 4n), was reinvestigated using gamma-ray coincidence data measured with the Gammasphere spectrometer. Previously, five high-spin rotational bands were discovered in this nucleus. The present reinvestigation revealed that the decay of band b1 is more complex than suggested in the earlier work and that it cannot be uniquely determined. Furthermore, a number of new transitions are added to the level scheme. The implications for the spin assignments and excitation energies of the five bands and for comparisons with cranked Nilsson-Strutinsky calculations are discussed.

Nuclear Data Sheets for A = 243

Available information pertaining to the nuclear structure of all nuclei with mass numbers A=243 is presented. Various decay and reaction data are evaluated and compared. Adopted data, levels, spin, parity and configuration assignments are given. When there are insufficient data, expected values from systematics of nuclear properties or/and theoretical calculations are quoted. Unexpected or discrepant experimental results are also noted. A summary and compilation of the discovery of various isotopes in this mass region is given in 2013Fr02 (243Np, 243Pu, 243Am, 243Cm, 243Bk, and 243Cf), 2011Me01 (243Es), and 2013Th02 (243Fm).

Ambitwistor strings in four dimensions.

We develop ambitwistor string theories for four dimensions to obtain new formulas for tree-level gauge and gravity amplitudes with arbitrary amounts of supersymmetry. Ambitwistor space is the space of complex null geodesics in complexified Minkowski space, and in contrast to earlier ambitwistor strings, we use twistors rather than vectors to represent this space. Although superficially similar to the original twistor string theories of Witten, Berkovits, and Skinner, these theories differ in the assignment of world sheet spins of the fields, rely on both twistor and dual twistor representatives for the vertex operators, and use the ambitwistor procedure for calculating correlation functions. Our models are much more flexible, no longer requiring maximal supersymmetry, and the resulting formulas for amplitudes are simpler, having substantially reduced moduli. These are supported on the solutions to the scattering equations refined according to helicity and can be checked by comparison with corresponding formulas of Witten and of Cachazo and Skinner.

Band head spin assignment of Tl isotopes of superdeformed rotational bands

Abstract The Variable Moment of Inertia (VMI) model is proposed for the assignment of band head spin of super deformed (SD) rotational bands, which in turn is helpful in the spin prediction of SD bands. The moment of inertia and stiffness parameter (C), were calculated by fitting the proposed transition energies. The calculated transition energies are highly dependent on the prescribed spins. The calculated and observed transition energies agree well when an accurate band head spin (I 0) is assigned. The results are in good agreement with other theoretical results reported in literature. In this paper, we have reported the band head spin value 16 rotational band of super deformed Tl isotopes.

2π1νstates populated inTe135fromBe9-induced reactions with aSn132beam

γ-ray transitions in 134Te, 135Te, and 136Te were measured from 9Be-induced reactions with a radioactive 132Sn beam at a sub-Coulomb barrier energy of 3 MeV per nucleon using particle-γ coincidence spectroscopy. The transitions were selected by gating on alpha-like particles in a CsI detector following a combination of (9Be,α1n), (9Be,α2n), and (9Be,α3n) incomplete fusion-evaporation reactions. Distorted-wave Born approximation calculations suggest little to no contribution from the (9Be,7He), (9Be,6He), and (9Be,5He) direct reactions.γ-ray transitions from previously known 2+⊗ν2f7/2 and 4+⊗ν2f7/2 multiplet members in 135Te are observed. A new γ ray is observed, assigned to the third-excited state in 135Te, and new 2+⊗ν2f7/2 multiplet members are suggested. In addition, spin assignments are made by using recent one-neutron transfer data. The updated experimental data for 135Te are compared to shell-model calculations for a relatively complete set of states up to the yrast 15/2−,4+⊗ν2f7/2 multiplet member at 1505 keV.Received 28 March 2014DOI:https://doi.org/10.1103/PhysRevC.90.014322©2014 American Physical Society

High-spin structure of odd-oddRe172

A significant extension of the level scheme for the odd-odd nucleus $^{172}\mathrm{Re}$ was accomplished through the use of the Gammasphere spectrometer. States up to a tentative spin assignment of 39 were observed and two new structures were identified. Configuration assignments are proposed based on alignment properties and observed band crossings.

Substituent effects on spin state in a series of mononuclear manganese(III) complexes with hexadentate Schiff-Base ligands.

Eleven new mononuclear manganese(III) complexes prepared from two hexadentate ligands, L1 and L2, with different degrees of steric bulk in the substituents are reported. L1 and L2 are Schiff bases resulting from condensation of N,N'-bis(3-aminopropyl)ethylenediamine with 3-methoxy-2-hydroxybenzaldehyde and 3-ethoxy-2-hydroxybenzaldehyde respectively, and are members of a ligand series we have abbreviated as R-Sal2323 to indicate the 323 alkyl connectivity in the starting tetraamine and the substitution (R) on the phenolate ring. L1 hosts a methoxy substituent on both phenolate rings, while L2 bears a larger ethoxy group in the same position. Structural and magnetic properties are reported in comparison with those of a previously reported analogue with L1, namely, [MnL1]NO3, (1e). The BPh4(-) and PF6(-) complexes [MnL1]BPh4, (1a), [MnL2]BPh4, (2a), [MnL1]PF6, (1b'), and [MnL2]PF6, (2b), with both ligands L1 and L2, remain high-spin (HS) over the measured temperature range. However, the monohydrate of (1b') [MnL1]PF6·H2O, (1b), shows gradual spin-crossover (SCO), as do the ClO4(-), BF4(-), and NO3(-) complexes [MnL1]ClO4·H2O, (1c), [MnL2]ClO4, (2c), [MnL1]BF4·H2O, (1d), [MnL2]BF4·0.4H2O, (2d), [MnL1]NO3, (1e), and [MnL2]NO3·EtOH, (2e). The three complexes formed with ethoxy-substituted ligand L2 all show a higher T1/2 than the analogous complexes with methoxy-substituted ligand L1. Analysis of distortion parameters shows that complexes formed with the bulkier ligand L2 exhibit more deformation from perfect octahedral geometry, leading to a higher T1/2 in the SCO examples, where T1/2 is the temperature where the spin state is 50% high spin and 50% low spin. Spin state assignment in the solid state is shown to be solvate-dependent for complexes (1b) and (2e), and room temperature UV-visible and NMR spectra indicate a solution-state spin assignment intermediate between fully HS and fully low spin in 10 complexes, (1a)-(1e) and (2a)-(2e).