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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Half-life of Ge 71 and the gallium anomaly

Recent discussions about the origin of the so-called gallium anomaly have motivated a remeasurement of the half-life of 71 Ge. Here, we have conducted three separate measurements using dedicated planar Ge detectors—one with 55 Fe as a standard, one with 57 Co as a standard, and one standalone 71 Ge measurement. Our results yield a half-life of 11.468±0.008 days, which is consistent with, but significantly more precise than, the currently accepted value. With this experiment, the potential explanation of the gallium anomaly being due to an unexpectedly long 71 Ge half-life has been ruled out, leaving the anomaly's origin as an open question.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Nuclear Data Sheets for A = 71

The evaluated spectroscopic data are presented for experimentally known nuclides of mass 71 (Mn,Fe,Co,Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr). Excited-state data are nonexistent for {sup 71}Mn, {sup 71}Fe, {sup 71}Co and {sup 71}Kr. Significant new data have been added since the last evaluation of A=71 nuclides by M. Bhat (1993Bh02). Excited states are now known in {sup 71}Ni and {sup 71}Cu, and enhanced information about high-spin excitations is available for {sup 71}Ga, {sup 71}As and {sup 71}Br. The decay schemes of radioactive isotopes {sup 71}Mn and {sup 71}Fe are not known at all, and those for {sup 71}Co, {sup 71m}Ni and {sup 71}Kr are not known well. For the decay of {sup 71}Cu, {sup 71g}Ni, and {sup 71}Br, extensive data are available, but in the opinion of the evaluators the decay schemes still seem incomplete. This work supersedes earlier full evaluations of A=71 published by 1988Bh01, 1979Ke06 and 1973Al33, and the last one published in 'update' mode by 1993Bh02.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Dynamical shift of NMR lines in nanostructured Ga–In–Sn melt

NMR spectrum and recovery of longitudinal nuclear magnetization after inverting pulses were measured for isotopes {sup 69}Ga and {sup 71}Ga in a liquid eutectic alloy Ga–In–Sn introduced in porous glasses having pores with the sizes of 25 and 7 nm. The measurements were conducted in the fields of 9.4, 11.7, and 17.6 T and compared with those for the bulk melt sample. Differences between the shape and position of the NMR lines in various fields and for different gallium isotopes were revealed in the melt introduced into the porous glass with the pores size of 7 nm. Data obtained for this sample were interpreted based on the theoretical model of dynamic quadrupolar shift, and correlation time of atomic motion was found within this model. Characteristics of the atomic motion calculated based on the dynamic shift model and from the spin relaxation data were shown to agree with each other.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2010

Coulomb excitation of {sup 73}Ga

The B(E2;I{sub i}{yields}I{sub f}) values for transitions in {sub 31}{sup 71}Ga{sub 40} and {sub 31}{sup 73}Ga{sub 42} were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of {sup 71,73}Ga at the REX-ISOLDE on-line isotope mass separator facility. The emitted {gamma} rays were detected by the MINIBALL {gamma}-detector array, and B(E2;I{sub i}{yields}I{sub f}) values were obtained from the yields normalized to the known strength of the 2{sup +}{yields}0{sup +} transition in the {sup 120}Sn target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N=40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N=40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2{sup -} spin and parity for the ground state, the extracted results revealed evidence for a 1/2{sup -},3/2{sup -} doublet near the ground state in {sub 31}{sup 73}Ga{sub 42} differing by at most 0.8 keV in energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Analysis of the transient response of nuclear spins in GaAs with/without nuclear magnetic resonance

As an alternative to studying the steady-state responses of nuclear spins in solid state systems, working within a transient-state framework can reveal interesting phenomena. The response of nuclear spins in GaAs to a changing magnetic field was analyzed based on the time evolution of nuclear spin temperature. Simulation results well reproduced our experimental results for the transient oblique Hanle signals observed in an all-electrical spin injection device. The analysis showed that the so called dynamic nuclear polarization can be treated as a cooling tool for the nuclear spins: It works as a provider to exchange spin angular momentum between polarized electron spins and nuclear spins through the hyperfine interaction, leading to an increase in the nuclear polarization. In addition, a time-delay of the nuclear spin temperature with a fast sweep of the external magnetic field produces a possible transient state for the nuclear spin polarization. On the other hand, the nuclear magnetic resonance acts as a heating tool for a nuclear spin system. This causes the nuclear spin temperature to jump to infinity: i.e., the average nuclear spins along with the nuclear field vanish at resonant fields of {sup 75}As, {sup 69}Ga and {sup 71}Ga, showing an interesting step-dip structure in the oblique Hanle signals. These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A Possible Liquid–Liquid Transition in a Ga–In Melt Introduced into an Opal Matrix

The temperature evolution of the Ga{sub 94}In{sub 6} liquid alloy introduced into an opal matrix has been studied by the NMR method in the temperature range 300–155 K. The temperature dependences of the position and the intensity of the NMR signals from {sup 71}Ga, {sup 69}Ga, and {sup 115}In isotopes have been measured upon cooling and heating of the nanocomposite. The {sup 71}Ga NMR line has been observed to be split into two components on cooling below 176 K with a transfer of the intensity to the high-frequency component. The results demonstrate an induced by nanoconfinement shift of the eutectic point in the alloy and the liquid–liquid phase transition in the indium depleted part of the melt.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Structural transformations in amorphous ↔ crystalline phase change of Ga-Sb alloys

Ga-Sb alloys with compositions ranging between ∼12 and 50 at. % Ga are promising materials for phase change random access memory applications. The short-range structures of two such alloys with compositions Ga{sub 14}Sb{sub 86} and Ga{sub 46}Sb{sub 54} are investigated, in their amorphous and crystalline states, using {sup 71}Ga and {sup 121}Sb nuclear magnetic resonance spectroscopy and synchrotron x-ray diffraction. The Ga and Sb atoms are fourfold coordinated in the as-deposited amorphous Ga{sub 46}Sb{sub 54} with nearly 40% of the constituent atoms being involved in Ga-Ga and Sb-Sb homopolar bonding. This necessitates extensive bond switching and elimination of homopolar bonds during crystallization. On the other hand, Ga and Sb atoms are all threefold coordinated in the as-deposited amorphous Ga{sub 14}Sb{sub 86}. Crystallization of this material involves phase separation of GaSb domains in Sb matrix and a concomitant increase in the Ga coordination number from 3 to 4. Results from crystallization kinetics experiments suggest that the melt-quenching results in the elimination of structural “defects” such as the homopolar bonds and threefold coordinated Ga atoms in the amorphous phases of these alloys, thereby rendering them structurally more similar to the corresponding crystalline states compared to the as-deposited amorphous phases.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Moissanite anvil cell design for giga-pascal nuclear magnetic resonance

A new design of a non-magnetic high-pressure anvil cell for nuclear magnetic resonance (NMR) experiments at Giga-Pascal pressures is presented, which uses a micro-coil inside the pressurized region for high-sensitivity NMR. The comparably small cell has a length of 22 mm and a diameter of 18 mm, so it can be used with most NMR magnets. The performance of the cell is demonstrated with external-force vs. internal-pressure experiments, and the cell is shown to perform well at pressures up to 23.5 GPa using 800 μm 6H-SiC large cone Boehler-type anvils. {sup 1}H, {sup 23}Na, {sup 27}Al, {sup 69}Ga, and {sup 71}Ga NMR test measurements are presented, which show a resolution of better than 4.5 ppm, and an almost maximum possible signal-to-noise ratio.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Resonance Structure of the Charge-Exchange Strength Function and Neutrino-Capture Cross Sections for the Isotopes {sup 71}Ga, {sup 98}Mo, and {sup 127}I

A resonance structure of the charge-exchange strength function S(E) and its effect on the neutrino-capture cross sections for the isotopes {sup 71}Ga, {sup 98}Mo, and {sup 127}I are studied within the self-consistent theory of finite Fermi systems. The calculation of the strength function S(E) takes into account Gamow–Teller, analog, and so-called lower lying pygmy resonances. The neutrino-capture cross sections σ(E) for the above three isotopes are calculated with allowance for the resonance structure of the strength function S(E), and the effect of each resonance on the energy dependence σ(E) is analyzed. It is found that all charge-exchange resonances in the strength function S(E) should be taken into account in calculating the neutrino-capture cross section σ(E) for the isotopes {sup 71}Ga, {sup 98}Mo, and {sup 127}I. The disregard of even highlying resonances leads to a substantial underestimation of the cross section σ(E), and this may affect the interpretation of respective experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Intermetallic solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3}: Synthesis, structure, NQR study and electronic band structure calculations

Unlimited solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3} was prepared from Ga flux. Its crystal structure was refined for Fe{sub 0.5}Co{sub 0.5}Ga{sub 3} (P4{sub 2}/mnm, a=6.2436(9), c=6.4654(13), Z=4) and showed no ordering of the metal atoms. A combination of the electronic band structure calculations within the density functional theory (DFT) approach and {sup 69,71}Ga nuclear quadrupole resonance (NQR) spectroscopy clearly shows that the Fe-Fe and Co-Co dumbbells are preferred to the Fe-Co dumbbells in the crystals structure. The band structure features a band gap of about 0.4 eV, with the Fermi level crossing peaks of a substantial density of electronic states above the gap for x>0. The solid solution is metallic for x>0.025. The study of the nuclear spin-lattice relaxation shows that the rate of the relaxation, 1/T{sub 1}, is very sensitive to the Co concentration and correlates well with the square of the density of states at the Fermi level, N{sup 2}(E{sub F}). - Graphical abstract: Rate of the nuclear spin-lattice relaxation, 1/T{sub 1}, observed in the {sup 69}Ga NQR experiments for the intermetallic solid solution Fe{sub 1-x}Co{sub x}Ga{sub 3} is the highest for x=0.25 with the highest calculated density of electronic states at the Fermi level, N(E{sub F}); in general, 1/T{sub 1} correlates with N{sup 2}(E{sub F}). Highlights: Black-Right-Pointing-Pointer Fe{sub 1-x}Co{sub x}Ga{sub 3} solid solution is prepared in single crystalline form from Ga flux. Black-Right-Pointing-Pointer In the crystal structure Fe-Fe and Co-Co dumbbells are preferred to Fe-Co dumbbells. Black-Right-Pointing-Pointer Metal-to-semiconductor transition occurs at 0<x<0.025. Black-Right-Pointing-Pointer {sup 69,71}Ga NQR spectra efficiently probe local environment of two independent Ga atoms. Black-Right-Pointing-Pointer Rate of nuclear spin-lattice relaxation follows squared DOS at the Fermi level.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Pseudogap and anharmonic phonon behavior in Ba{sub 8}Ga{sub 16}Ge{sub 30}: An NMR study

We have performed {sup 69}Ga, {sup 71}Ga, and {sup 137}Ba NMR on Ba{sub 8}Ga{sub 16}Ge{sub 30}, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Local environment and composition of magnesium gallium layered double hydroxides determined from solid-state {sup 1}H and {sup 71}Ga NMR spectroscopy

Ordering of gallium(III) in a series of magnesium gallium (MgGa) layered double hydroxides (LDHs), [Mg{sub 1−x}Ga{sub x}(OH){sub 2}(NO{sub 3}){sub x}·yH{sub 2}O] was investigated using solid-state {sup 1}H and {sup 71}Ga NMR spectroscopy as well as powder X-ray diffraction. Three different proton environments from Mg{sub 3}-OH, Mg{sub 2}Ga-OH and intergallery water molecules were assigned and quantified using ({sup 1}H,{sup 71}Ga) HETCOR and {sup 1}H MAS NMR. A single {sup 71}Ga site originating from the unique Ga site in the MgGa LDH's was observed in {sup 71}Ga MAS and 3QMAS NMR spectra. Both {sup 1}H MAS NMR spectra recorded at 21.1 T (900 MHz) and elemental analysis show that the synthesized MgGa LDH's had a lower Mg:Ga ratio than that of the starting reactant solution. The origin of this is the formation of soluble [Ga(OH){sub 4}]{sup −} complexes formed during synthesis, and not due to formation of insoluble gallium (oxy)hydroxides. No sign of Ga-O-Ga connectivities or defects were detected for the MgGa LDH's. - Graphical abstract: Two types of hydroxides groups are observed in magnesium gallium layered double hydroxides revealing an ordering of Ga in the cation layer. - Highlights: • Ga is ordered in our magnesium gallium layered double hydroxides. • Ga depletion due to formation of soluble Ga complexes during synthesis. • No sign of Ga rich regions in magnesium gallium LDHs. • Solid state {sup 1}H and {sup 71}Ga give detailed insight into the structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Gallium neutrino absorption cross section and its uncertainty

In the recent Baksan Experiment on Sterile Transitions (BEST), a suppressed rate of neutrino absorption on a gallium target was observed, consistent with earlier results from neutrino source calibrations of the SAGE and GALLEX/GNO solar neutrino experiments. The BEST Collaboration, utilizing a 3.4 MCi 51 Cr neutrino source, found observed-to-expected counting rates at two very short baselines of 𝑅 = 0.791 ± 0.05 and 0.766 ± 0.05, respectively. Among recent neutrino experiments, BEST is notable for the simplicity of both its neutrino spectrum, line neutrinos from an electron-capture source whose intensity can be measured to a estimated precision of 0.23%, and its absorption cross section, where the precisely known rate of electron capture to the gallium ground state, 71 Ge ⁢(𝑒−, 𝜈 𝑒 )⁢ 71 Ga ⁢(g.s.), establishes a minimum value. However, the absorption cross section uncertainty is a common systematic in the BEST, SAGE, and GALLEX/GNO neutrino source experiments. Here, in this work, we update that cross section, considering a variety of electroweak corrections and the role of transitions to excited states, to establish both a central value and reasonable uncertainty, thereby enabling a more accurate assessment of the statistical significance of the gallium anomalies. Results are given for 51 Cr and 37 Ar sources. The revised neutrino capture rates are used in a reevaluation of the BEST and gallium anomalies.

electroweak interactions in nuclear physics↗
DOE OSTI2023

Photonuclear Production of 67 Cu From Gallium

Copper-67 is a radioisotope of interest for medical imaging and therapy as well as for under- standing stellar and interstellar evolution pertaining to the formation of proton-rich nuclei. Since 67 Cu decays 100% to 67 Zinc, understanding this reaction can shed light on the abundance of this and other p-nuclei elements in the universe. Here, the photonuclear production of 67 Cu from 71 Ga and natural gallium is examined as an alternative to its photoproduction from zinc. Two research and development production runs were performed at Thomas Jefferson National Accelerator Facility using an electron linac. During the first run, an 805-W, 30.9-MeV beam was used to irradiate a 1-mm tungsten radiator to create a bremsstrahlung flux. The resulting gamma photons irradiated 50.9 g of natural gallium encased in a graphite crucible for 24.2 h; 7.02 Bq/W∙s∙kg of 67 Cu activity was produced. During the second run, a 4380-W, 31.5-MeV beam was used for 12.0 h on the same target containing 60 g of natural gallium; 6.41 Bq/W∙s∙kg of 67 Cu activity was produced. Because of the difficulties in spectroscopically differentiating 67 Cu from 67 Ga, prior to each run, an isotopically pure 71 Ga disk was irradiated using a 100-W beam for 1 h, at the same respective energies. Finally, these baseline irradiations allowed for separation of 67 Cu from 67 Ga in the spectroscopic measurements of the natural gallium targets.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

Characterization of elastic interactions in GaAs/Si composites by optically pumped nuclear magnetic resonance

Elastic interactions in GaAs/Si bilayer composite structures were studied by optically pumped nuclear magnetic resonance (OPNMR). The composites were fabricated by epoxy bonding of a single crystal of GaAs to a single crystal of Si at 373 K followed by selective chemical etching of the GaAs at room temperature to obtain a series of samples with GaAs thickness varying from 37 μm to 635 μm, while the Si support thickness remained fixed at 650 μm. Upon cooling to below 10 K, a biaxial tensile stress developed in the GaAs film due to differential thermal contraction. The strain perpendicular to the plane of the bilayer and localized near the surface of the GaAs was deduced from the quadrupolar splitting of the Gallium-71 OPNMR resonance. Strain relaxation by bowing of the composite was observed to an extent that depended on the relative thickness of the GaAs and Si layers. The variation of the strain with GaAs layer thickness was found to be in good agreement with a general analytical model for the elastic relationships in composite media.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Cation substitution in β-tricalcium phosphate investigated using multi-nuclear, solid-state NMR

The substitution of aluminium, gallium and sodium cations into β-tricalcium phosphate (β-TCP; Ca{sub 3}(PO{sub 4}){sub 2}) has been investigated, and the Ca sites involved successfully determined, using a combination of 1D {sup 31}P, {sup 27}Al, {sup 71}Ga, {sup 23}Na and {sup 43}Ca (natural abundance) NMR and 2D {sup 27}Al({sup 31}P), {sup 71}Ga({sup 31}P) and {sup 23}Na({sup 31}P) rotary-resonance-recoupled heteronuclear multiple-quantum correlation (R{sup 3}-HMQC) NMR. Over the compositional range studied, substitution of Ca{sup 2+} by Al{sup 3+} or Ga{sup 3+} was observed only on the Ca(5) site, whilst substitution by Na{sup +} was confined to the Ca(4) site. Some AlPO{sub 4} or GaPO{sub 4} second phase was observed at the highest doping levels in the Al{sup 3+} and Ga{sup 3+} substituted samples. - Graphical abstract: 2D contour plots with skyline projections showing recoupling of {sup 27}Al, {sup 71}Ga and {sup 23}Na to different {sup 31}P sites. - Highlights: • β-Ca{sub 3}(PO{sub 4}){sub 2} has been prepared pure and also with Al{sup 3+}, Ga{sup 3+} and Na{sup +} substituents. • Multi-nuclear 1D NMR and heteronuclear X({sup 31}P) recoupling have been used. • Models for substitution correctly predict site preference and occupancy. • Progressive changes in {sup 31}P spectra have been explained. • Al{sup 3+} and Ga{sup 3+} substitute onto the Ca(5) site, and Na{sup +} onto the Ca(4) site.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Absolute shielding scales for Al, Ga, and In and revised nuclear magnetic dipole moments of {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In nuclei

We present coupled cluster calculations of NMR shielding constants of aluminum, gallium, and indium in water-ion clusters. In addition, relativistic and dynamical corrections and the influence of the second solvation shell are evaluated. The final NMR shielding constants define new absolute shielding scales, 600.0 ± 4.1 ppm, 2044.4 ± 31.4 ppm, and 4507.7 ± 63.7 ppm for aluminum, gallium, and indium, respectively. The nuclear magnetic dipole moments for {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In isotopes are corrected by combining the computed shielding constants with experimental NMR frequencies. The absolute magnitude of the correction increases along the series and for indium isotopes it reaches approximately −8.0 × 10{sup −3} of the nuclear magneton.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗