Knockout and fragmentation reactions using a broad range of tin isotopes
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Rodríguez-Sánchez, J. L.↗
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Redox and structural controls on tin isotopic fractionations among magmas
Recent analytical developments have made possible the determination of the isotopic composition of tin in igneous rocks. In order to establish a framework to interpret the mass-dependent tin isotopic signatures of planetary materials, in this work, seven geologically-relevant silicate glasses (basalt, rhyolite, enstatite and anorthite glasses) were synthesized with moderate amounts of 119 Sn (on the order of a weight percent). Redox conditions were controlled during sample synthesis to set the redox ratio (Sn 2+ /Sn tot ) from stannous (Sn 2+ ) to stannic (Sn 4+ ) glasses. The mean force constants of tin bonds in these glasses were determined by synchrotron nuclear resonant inelastic X-ray scattering (NRIXS) in order to determine the reduced isotopic partition function ratios (β-factors) of these glasses. Clues on the coordination chemistry and the valence state of tin in these glasses were also derived from synchrotron Mossbauer spectroscopy (SMS). The force constants of tin drastically increases from Sn 2+ -bearing to Sn 4+ -bearing glasses and varies significantly with the glass composition at a given redox state. The average coordination number of tin likely controls these variations with glass composition as suggested by SMS results. It is concluded that large isotope fractionation is expected between materials containing Sn 2+ and Sn 4+ respectively even at magmatic temperatures and that the coordination chemistry of tin in silicates strongly affect its isotope partitioning behavior. Our experimental data are finally used to interpret available Sn isotope data collected in terrestrial rocks. The incompatible behavior of Sn 4+ in mantle minerals leads to a enrichment in heavy isotopes in mantle melts and to the depletion in heavy isotopes in solid residues of melting with a magnitude consistent with the isotope fractionation between Sn 2+ and Sn 4+ predicted by NRIXS data. Finally, we show that during fractional crystallization of basalt and considering the effect of tin coordination number in minerals and melts, the partitioning of Sn 4+ into ilmenite leads to an enrichment in light isotopes in the residual melt.
58 GEOSCIENCES↗
Dispersive optical-model potential for protons in 100 ⩽ A ⩽ 132 even–even tin isotopes
Data on single-particle energies, differential elastic-scattering cross sections, and total cross sections for proton-induced reactions on stable tin isotopes were analyzed on the basis of the dispersive optical model. Good agreement with experimental data was obtained by setting the parameters of the dispersive optical potential to values averaged over the tin isotopic chain and by assuming that the dependence of surface absorption on the neutron–proton asymmetry is close to a traditional dependence. Predictive calculations for single-particle proton spectra and total reaction cross sections were performed for the doubly magic isotopes {sup 100,132}Sn. The calculated values of the energy gap between the 1h{sub 11/2}–1g{sub 7/2} and 1g{sub 7/2}–2d{sub 5/2} states were found to be in good agreement with the results of calculations performed with allowance for the tensor component of the effective nucleon–nucleon interaction.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Neutron occupancies and single-particle energies across the stable tin isotopes
The occupancies and vacancies of the valence neutron orbitals across the stable tin isotopic chain from 112 ≤ A ≤ 124 have been determined. These were inferred from the cross sections of neutron adding and -removing reactions. In each case, the reactions were chosen to have good angular momentum matching for transfer to the low- and high-` orbitals present in this valence space. Here, these new data are compared to older systematic studies. The effective single-neutron energies are determined by combining information from energy centroids determined from the adding and removing reactions. Two of the five orbitals are nearly degenerate, below N = 64, and approximately two MeV more bound than the other three, which are also degenerate.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Elastic and inelastic scattering of 40-mev alpha particles from even tin isotopes
Angular distributions measured for elastic and inelastic scattering of 40-MeV alpha particles from even tin isotopes
TIN↗
Comparative analysis of cross sections of residual nuclei on separated tin isotopes at a beam energy of protons and deuterons 3.65 GeV/nucleon
The cross sections of residual nuclei in the separated tin isotopes ({sup 112}Sn, {sup 118}Sn, {sup 120}Sn, and {sup 124}Sn), irradiated with proton and deuteron beams with energy 3.65 GeV/nucleon, are investigated. Parametrization by ten parametric semi-empirical formula was conducted with the aim of determining the total cross sections and analyzing the measurement results. The dependence of total inelastic cross sections on the mass number of the target and the structure of the incoming particle was investigated via the comparison of the obtained data.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Erratum: Informing direct neutron capture on tin isotopes near the N = 82 shell closure [Phys. Rev. C 99 , 041302(R) (2019)]
Erratum to "Informing direct neutron capture on tin isotopes near the N = 82 shell closure [Phys. Rev. C 99, 041302(R) (2019)]
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Charge Radii Measurements of Exotic Tin Isotopes in the Proximity of 𝑁 =50 and 𝑁 =82
We report nuclear charge radii for the isotopes 104–134 Sn , measured using two different collinear laser spectroscopy techniques at ISOLDE-CERN. These measurements clarify the archlike trend in charge radii along the isotopic chain and reveal an odd-even staggering that is more pronounced near the 𝑁 =50 and 𝑁 =82 shell closures. The observed local trends are well described by both nuclear density functional theory and valence space in-medium similarity renormalization group calculations. Both theories predict appreciable contributions from beyond-mean-field correlations to the charge radii of the neutron-deficient tin isotopes. The models, however, fall short of reproducing the magnitude of the known 𝐵(𝐸2) transition probabilities, highlighting the remaining challenges in achieving a unified description of both ground-state properties and collective phenomena.
laser spectroscopy↗
Charge radii measurements of exotic tin isotopes in the proximity of $N=50$ and $N=82$
We report nuclear charge radii for the isotopes $^{104-134}$Sn, measured using two different collinear laser spectroscopy techniques at ISOLDE-CERN. These measurements clarify the archlike trend in charge radii along the isotopic chain and reveal an odd-even staggering that is more pronounced near the $N=50$ and $N=82$ shell closures. The observed local trends are well described by both nuclear density functional theory and valence space in-medium similarity renormalization group calculations. Both theories predict appreciable contributions from beyond-mean-field correlations to the charge radii of the neutron-deficient tin isotopes. The models fall short, however, of reproducing the magnitude of the known $B(E2)$ transition probabilities, highlighting the remaining challenges in achieving a unified description of both ground-state properties and collective phenomena.
FOS: Physical sciences↗
Connecting Nuclear Structure to Stellar Astrophysics: Neutron Skin in Tin Isotopes
The first observation of a neutron star merger by the LIGO-Virgo collaboration in 2017 highlights the need to improve our fundamental understanding of the equation of state of dense, neutron rich matter. The origin of heavy elements in the r-process and the structure of neutron stars are governed by the properties of neutron rich matter, for which experimental data is limited. Further analysis of this historic event and all future neutron star mergers relies on constraining the nuclear equation of state with experimental observables. We propose a novel method for systematically studying the evolution of the neutron skin in stable tin isotopes, by measuring the low-energy nuclear dipole strength over the broadest possible range of neutron-to-proton ratios in a single element. Nuclear resonance fluorescence with 100% linearly polarized photons from the High Intensity Gamma-ray Source (HIGS) facility was used to selectively measure the E1 photoabsorption strength of 112 Sn and 124 Sn at excitation energies from 3.5 MeV up to neutron separation, where the Pygmy Dipole Resonance dominates. The dipole polarizabilities of 112 Sn and 124 Sn were measured to be 9.03 ± 0.23 fm 3 and 9.11 ± 0.24 fm 3 , respectively. These uniquely systematically consistent measurements provide highly accurate experimental data for improving microscopic nuclear models as well as calculations of astrophysical nucleosynthesis and neutron star structure.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
(n,{gamma}) Experiments on tin isotopes
Neutron capture experiments on highly enriched {sup 117,119}Sn isotopes were performed with the DANCE detector array located at the Los Alamos Neutron Science Center. The DANCE detector provides detailed information about the multi-step {gamma}-ray cascade following neutron capture. Analysis of the experimental data provides important information to improve understanding of the neutron capture reaction, including a test of the statistical model, the assignment of spins and parities of neutron resonances, and information concerning the Photon Strength Function (PSF) and Level Density (LD) below the neutron separation energy. Preliminary results for the (n,{gamma}) reaction on {sup 117,119}Sn are presented. Resonance spins of the odd-A tin isotopes were almost completely unknown. Resonance spins and parities have been assigned via analysis of the multi-step {gamma}-ray spectra and directional correlations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Investigation into the semimagic nature of the tin isotopes through electromagnetic moments
A complete set of electromagnetic moments, B(E2;0 + 1 2 + 1 ), Q(2 + 1 ), and g(2 + 1 ), have been measured from Coulomb excitation of semi-magic 112,114,116,118,120,122,124 Sn (Z = 50) on natural carbon and titanium targets. The magnitude of the B(E2) values, measured to a precision of ~4%, disagree with a recent lifetime study [Phys. Lett. B 695, 110 (2011)] that employed the Doppler- shift attenuation method. The B(E2) values show an overall enhancement compared with recent theoretical calculations and a clear asymmetry about midshell, contrary to naive expectations. A new static electric quadrupole moment, Q(2 + 1 ), has been measured for 114 Sn. The static quadrupole moments are generally consistent with zero but reveal an enhancement near midshell; this had not been previously observed. The magnetic dipole moments are consistent with previous measurements and show a near monotonic decrease in value with neutron number. The current theory calculations fail to reproduce the electromagnetic moments of the tin isotopes. The role of 2p-2h and 4p-4h intruders, which are lowest in energy at mid shell and outside of current model spaces, needs to be investigated in the future.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Interaction of {sup 12}C ions with nuclei of enriched tin isotopes at an energy of 2.2 GeV per nucleon
The formation cross sections for about 110 products of interaction between a {sup 12}C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes {sup 112,118,120,124}Sn were calculated. Massyield and charge distributions were obtained for {sup 112,118,124}Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Z{sub p}, are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions are compared for proton-, deuteron- and ion-nucleus reactions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Formation of close-to-target products in reactions induced by {sup 12}C ions on tin isotopes at the energy of 2.2 GeV per nucleon
Cross sections for charge-exchange reactions induced by the interaction between {sup 12}C ions of energy E{sub 12{sub C}} = 2.2 GeV per nucleon and tin targets enriched in the isotopes {sup 118,120,124}Sn were measured by the induced-activity method. The cross sections for products whose charge numbers were in excess of the target charge number (Sb and Te) were determined. The shape of the isotope distribution of Sb products was indicative of the evaporative character of neutron emission in the formation of final-state products. The dependence of cross sections for charge-exchange reactions on the nucleonic composition of the target was considered. The contribution of electromagnetic excitation to the cross section for the reaction {sup 124}Sn({sup 12}C, x){sup 124}Sn was estimated.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Informing direct neutron capture on tin isotopes near the N = 82 shell closure
Half of the elements heavier than iron are believed to be produced through the rapid neutron-capture process ($r$-process). The astrophysical environment(s) where the $r$-process occurs remains an open question, even after recent observations of neutron-star mergers and the associated kilonova. Features in the abundance pattern of $r$-process ashes may provide critical insight for distinguishing contributions from different possible sites, including neutron-star mergers and core-collapse supernovae. In particular, the largely unknown neutron-capture reaction rates on neutron-rich unstable nuclei near 132 Sn could have a significant impact on the final $r$-process abundances. To better determine these neutron-capture rates, the ($d,p$) reaction has been measured in inverse kinematics using radioactive ion beams of 126 Sn and 128 Sn and a stable beam of 124 Sn interacting with a (CD 2 )$_n$ target. An array of position-sensitive silicon strip detectors, including the Super Oak Ridge Rutgers University Barrel Array, was used to detect light reaction products. In addition to the present measurements, previous measurements of 130,132 Sn($d,p$) were reanalyzed using state-of-the-art reaction theory to extract a consistent set of spectroscopic factors for ($d,p$) reactions on even tin nuclei between the heaviest stable isotope 124 Sn and doubly magic 132 Sn. The spectroscopic information was used to calculate direct-semidirect ($n,γ$) cross sections, which will serve as important input for r-process abundance calculations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Evolution of the dipole polarizability in the stable tin isotope chain
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74 ATOMIC AND MOLECULAR PHYSICS↗
Shape polarization in the tin isotopes near N = 60 from precision g-factor measurements on short-lived 11/2 - isomers
The g factors of 11/2 - isomers in semimagic 109 Sn and 111 Sn (isomeric lifetimes $\tau$ = 2.9(3) ns and $\tau$ = 14.4(7) ns, respectively) were measured by an extension of the Time Differential Perturbed Angular Distribution technique, which uses LaBr3 detectors and the hyperfine fields of a gadolinium host to achieve precise measurements in a new regime of short-lived isomers. The results, g(11/2 - ; 109 Sn) = -0.186(8) and g(11/2 - ; 111 Sn) = -0.214(4), are significantly lower in magnitude than those of the 11/2 - isomers in the heavier isotopes and depart from the value expected for a near pure neutron h 11/2 configuration. Broken-symmetry density functional theory calculations applied to the sequence of 11/2 - states reproduce the magnitude and location of this deviation. The g(11/2 - ) values are affected by shape core polarization; the odd Oh 11/2 neutron couples to J π = 2 + , 4 + , 6 + ... configurations in the weakly-deformed effective core, causing a decrease in the g-factor magnitudes.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Structure of the Lightest Tin Isotopes
Here, we link the structure of nuclei around 100 Sn, the heaviest doubly magic nucleus with equal neutron and proton numbers (N=Z=50), to nucleon-nucleon (NN) and three-nucleon (NNN) forces constrained by data of few-nucleon systems. Our results indicate that 100 Sn is doubly magic, and we predict its quadrupole collectivity. We present precise computations of 101 Sn based on three-particle–two-hole excitations of 100 Sn, and we find that one interaction accurately reproduces the small splitting between the lowest J π = 7/2 + and 5/2 + states.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗