Germanium Nuclei Research Articles

Constraints on Elastic Neutrino Nucleus Scattering in the Fully Coherent Regime from the CONUS Experiment.

We report the best limit on coherent elastic scattering of electron antineutrinos emitted from a nuclear reactor off germanium nuclei. The measurement was performed with the CONUS detectors positioned at 17.1m from the 3.9 GW_{th} reactor core of the nuclear power plant in Brokdorf, Germany. The antineutrino energies of less than 10MeV assure interactions in the fully coherent regime. The analyzed dataset includes 248.7kgd with the reactor turned on and background data of 58.8kgd with the reactor off. With a quenching parameter of k=0.18 for germanium, we determined an upper limit on the number of neutrino events of 85 in the region of interest at 90%confidence level. This new CONUS dataset disfavors quenching parameters above k=0.27, under the assumption of standard-model-like coherent scattering of the reactor antineutrinos.

Triaxiality in selenium-76

Background: Selenium and germanium nuclei are associated with both triaxiality and shape coexistence. The relative influence of these deformation effects on the low-lying nuclear structure remains the subject of much discussion with additional attention drawn to $^{76}\mathrm{Se}$ and $^{76}\mathrm{Ge}$ due to the potential for the observation of neutrinoless double-$\ensuremath{\beta}$ decay.Purpose: Experimental observables related to the deformation of $^{76}\mathrm{Se}$ are lacking in precision. The purpose of the present paper is to provide electric quadrupole matrix elements with improved precision in order to determine the deformation of low-lying states in a model-independent manner.Methods: Sub-barrier Coulomb excitation was employed at the reaccelerated beam facility of the National Superconducting Cyclotron Laboratory using the JANUS setup. Using this method nineteen $E2$ matrix elements were extracted.Results: Extracted matrix elements agree within uncertainties with those in the literature but with improved precision. Through both a comparison with geometric models and a model-independent evaluation of $E2$ matrix elements using rotational invariants, the ground state of $^{76}\mathrm{Se}$ is best described as having a significant triaxial component, but is not maximally triaxially deformed.Conclusions: Selenium-76 exhibits a significant degree of triaxiality in its ground state. A detailed comparison with configuration-interaction calculations indicates that this can be well reproduced theoretically.

Search for low-mass dark matter with CDMSlite using a profile likelihood fit

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) searches for interactions between dark matter particles and germanium nuclei in cryogenic detectors. The experiment has achieved a low energy threshold with improved sensitivity to low-mass (<10 GeV/c$^2$) dark matter particles. We present an analysis of the final CDMSlite data set, taken with a different detector than was used for the two previous CDMSlite data sets. This analysis includes a data "salting" method to protect against bias, improved noise discrimination, background modeling, and the use of profile likelihood methods to search for a dark matter signal in the presence of backgrounds. We achieve an energy threshold of 70 eV and significantly improve the sensitivity for dark matter particles with masses between 2.5 and 10 GeV/c$^2$ compared to previous analyses. We set an upper limit on the dark matter-nucleon scattering cross section in germanium of 5.4$\times$10$^{-42}$ cm$^2$ at 5 GeV/c$^2$, a factor of $\sim$2.5 improvement over the previous CDMSlite result.

Consistent empirical physical formula construction for recoil energy distribution in HPGe detectors by using artificial neural networks

The gamma-ray tracking technique is one of the highly efficient detection method in experimental nuclear structure physics. On the basis of this method, two gamma-ray tracking arrays, AGATA in Europe and GRETA in the USA, are currently being developed. The interactions of neutrons in these detectors lead to an unwanted background in the gamma-ray spectra. Thus, the interaction points of neutrons in these detectors have to be determined in the gamma-ray tracking process in order to improve photo-peak efficiencies and peak-to-total ratios of the gamma-ray peaks. Therefore, the recoil energy distributions of germanium nuclei due to inelastic scatterings of 1-5 MeV neutrons were obtained both experimentally and using artificial neural networks. Also, for highly nonlinear detector response for recoiling germanium nuclei, we have constructed consistent empirical physical formulas (EPFs) by appropriate layered feed-forward neural networks (LFNNs). These LFNN-EPFs can be used to derive further physical functions which could be relevant to determination of neutron interactions in gamma-ray tracking process.

Skyrme force-like extension of the nuclear pairing interaction

In this paper, isovector and isoscalar pairing correlations were investigated using generalized Bardeen–Cooper–Shrieffer theory and a Skyrme force-like form of the residual interaction. The calculations are done for even–even N∼Z germanium nuclei in an axially symmetric Skyrme–Hartree–Fock + BCS scheme with SIII force and time-reversal invariance. A coexistence of T=0 and T=1 superfluid phases is observed.

High-resolution solid-state 73Ge NMR spectra of hexacoordinated germanium compounds.

High-resolution solid-state magic angle spinning 73Ge NMR spectra of hexavalent germanium compounds, i.e. diiodogermylene (1a) and bis(1-pyrrolyl)(meso-tetraphenylporphyrinato)germanium (3a), were determined. To the best of our knowledge, this is the first example of high-resolution solid-state 73Ge NMR spectra of hexacoordinated germanium nuclei. The symmetry requirement for observation of high-resolution solid-state 73Ge NMR spectra is discussed.

Low Temperature Gas Phase Synthesis of Germanium Nanowires

ABSTRACTSingle crystal Ge nanowires (NWs) were obtained in high yield by gas phase decomposition of germanium di-cyclopentadienylide ([Ge(C5H5)2]), at 325 °C on iron substrates. Highresolution electron microscopy (SEM/TEM) showed Ge NWs to be uniform in terms of diameter (20 nm) and length (&gt; 25 μm). The wire growth is selective and appears to be governed by a Ge-Fe alloy epilayer formed by the reaction between Ge clusters and iron substrate, during the initial stages of the CVD process. The supersaturation of Ge-Fe solid-solution with respect to Ge content induces the spontaneous formation of single crystal germanium nuclei that act as templates for the nanowire growth. X-ray and electron diffraction revealed the NWs to be single crystals of cubic germanium with a preferred growth direction[11–2]. The proposed base-growth model on Fe substrate is supported by TEM, EDX and XPS studies.

Molecular trapping of nuclei produced in neutrino capture reactions

We consider the reaction ν+ 71 Ga → 71 Ge+e − induced by solar neutrinos for the case that gallium is bound in a Ga 2 molecule. We find that about 30% of the germanium nuclei remain trapped in molecular GaGe systems.

NMR Spectra of Organogermanium Compounds. VI. NMR Spectra and Molecular Mechanics Calculations of 3-Methyl- and 3,3-Dimethylgermacyclohexanes

Abstract Several 3-methyl- or 3,3-dimethylgermacyclohexanes were prepared and their 13C and 73Ge NMR spectra were determined. Steric energies for all of stereoisomers of some of these germacyclohexanes were calculated by MM2 program. The effect of axial 3-methyl group of germacyclohexanes upon its C-5 is much the same with the corresponding effect in cyclohexanes, and is much smaller than the effect caused by axial methyl on germanium upon C-3,5. A large upfield shift is recorded for germanium nuclei when there is an axial methyl on C-3 of germacyclohexanes.

Relaxation mechanism of germanium-73 nuclei in tetrahalogermanes

The /sup 73/Ge spin-lattice relaxation time (T/sub 1/) and spin-spin relaxation time (T/sub 2/) if such tetrahalogermanes as GeCl/sub 4/, GeBr/sub 4/, and GeI/sub 4/ have been measured as a function of temperature. It has been shown that the germanium nuclei in GeCl/sub 4/ and GeBr/sub 4/ relax solely via the quadrupole relaxation mechanism for T/sub 1/ and via a combination of the quadrupole and the scalar coupling relaxation mechanisms for T/sub 2/. On the other hand, both the spin-lattice and the spin-spin relaxations for germanium nuclei in GeI/sub 4/ were solely via the quadrupole relaxation mechanism at room temperature. The viscosities of tetrahalogermane solutions were measured to obtain the reorientational correlation time. The reorientational correlation times (tau/sub c/) of GeCl/sub 4/ and GeBr/sub 4/ were 0.78 x 10/sup -11/ and 1.8 x 10/sup -11/ s at 30/sup 0/C, respectively, and the activation energies 9.6 and 11.2 kJmol/sup -1/, respectively. The scalar coupling constant J(/sup 73/Ge-/sup 35/Cl), was calculated as 24 Hz by using T/sub 2/ of /sup 35/Cl in GeCl/sub 4/. 29 references, 4 figures, 6 tables.

Investigation of the decay rate for71Ge in chemical compounds and calibration of the Mössbauer isomer shift of the 67 keV γ-transition of73Ge

Changes of the radioactive decay rate of71Ge (T1/2=11.43 days) have been studied experimentally for71Ge in some compounds of bivalent and quadrivalent germanium. Relative changes Δλ/λ of the electron capture probability have been measured, and the chemical changes Δρ(0) of the electron density at the germanium nuclei have been determined from these measurements. Values for the Mossbauer isomer shift calibration constants for the 67 keV γ-transition of73Ge have been estimated:C=δ/Δρ(0)=(0.061±0.020) mm·s−1/a.u., Δ〈r2〉=(21±7)·10−3 fm2, ΔR/R=(6.9±2.3)·10−4.

NMR spectra of organogermanium compounds. 5. Relaxation mechanism of germanium-73 nuclei in tetraalkylgermanes

The XTGe spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) in such alkylgermanes as symmetrical GeR4 (R = methyl, ethyl, n-propyl, n-butyl) and the unsymmetrical germacyclohexane derivatives 1,1,3-trimethyl-, 1,1,4-trimethyl-, and 1,1,3,5-tetramethyl-1-germacyclohexane have been measured at several temperatures in order to elucidate the relaxation mechanism of germanium nuclei in organogermanium compounds. Furthermore, the viscosities of the solutions of symmetrical alkylgermanes were measured to obtain the reorientational correlation times. T1 and T2 are the same for all the compounds investigated at room temperature, and these become shorter as the molecular radii become larger. The relaxation times of unsymmetrical germacyclohexane derivatives are even shorter than those of symmetrical GeR4. T1 and T2 of germanium nuclei in alkylgermanes were found to be dominated by the quadrupole relaxation. The reorientational correlation times ((0.69-10.9) x 10 s) and the activation energies (9.6-13.2 kJ/mol) for GeR4 are also discussed. 35 references, 5 figures, 2 tables.

Alpha-particle transfer to0+states in the germanium nuclei and the role of proton pairing correlations

Alpha transfer to the ground and first excited ${0}^{+}$ states of the Ge isotopes has been studied by means of the $^{64,66,68,70}\mathrm{Zn}(^{6}\mathrm{Li}, d)^{68,70,72,74}\mathrm{Ge}$ reactions at 34-MeV incident energy. The sharp variation in strength between $^{72}\mathrm{Ge}$ and $^{74}\mathrm{Ge}$ is shown to result from a change in the proton structure of these two isotopes as the neutron number changes from $N=40 \mathrm{to} 42$.NUCLEAR REACTIONS $^{64,66,68,70}\mathrm{Zn}(^{6}\mathrm{Li}, d)^{68,70,72,74}\mathrm{Ge}$, $E=34$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$ for ${0}^{+}$ states, DWBA analysis, deduced $S$.

Evidence of a spherical to prolate shape transition in the germanium nuclei

Evidence of a spherical (or oblate) to prolate shape transition around $N=40$ in even-$A$ germanium nuclei has been obtained by measuring the static quadrupole moments of the first ${2}^{+}$ excited states of $^{70}\mathrm{Ge}$, $^{72}\mathrm{Ge}$, $^{74}\mathrm{Ge}$, and $^{76}\mathrm{Ge}$ using the reorientation effect in Coulomb excitation. The measurements yield ${Q}_{{2}^{+}}$ values of $(+0.03\ifmmode\pm\else\textpm\fi{}0.06) or (+0.09\ifmmode\pm\else\textpm\fi{}0.06)e$b for $^{70}\mathrm{Ge}$, $(\ensuremath{-}0.13\ifmmode\pm\else\textpm\fi{}0.06)e$b for $^{72}\mathrm{Ge}$, $(\ensuremath{-}0.25\ifmmode\pm\else\textpm\fi{}0.06)e$b for $^{74}\mathrm{Ge}$, and $(\ensuremath{-}0.19\ifmmode\pm\else\textpm\fi{}0.06)e$b for $^{76}\mathrm{Ge}$.NUCLEAR REACTIONS $^{70}\mathrm{Ge}$($^{6}\mathrm{Li}$, $^{6}\mathrm{Li}$\ensuremath{'}), $E=10.5$ MeV; $^{72,74,76}\mathrm{Ge}(\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}})$, $E=7.0$ MeV; $^{70,72,74,76}\mathrm{Ge}$($^{16}\mathrm{O}$, $^{16}\mathrm{O}$\ensuremath{'}), $E=29.9$ MeV; measured $\ensuremath{\sigma}(E, {E}_{^{16}\mathrm{O}^{\ensuremath{'}}})$ deduced ${Q}_{{2}^{+}}$, $B(E2; {0}^{+}\ensuremath{\rightarrow}{2}^{+})$. Enriched targets.

Ge72,74,76by the (t,p) reaction

A systematic study of all of the stable even germanium isotopes by the ($t$,$p$) reaction has been performed. The reaction protons were analyzed in a quadrupole-dipole-dipole-dipole spectrometer with a resulting energy resolution approximately 15 keV. Levels up to 3 MeV in excitation energy were measured and the angular distributions compared to distorted wave analysis. A number of new spin assignments are made in the heavier germanium nuclei. Examination of the systematic trend of the ground state as well as various excited levels strongly supports a transition in nuclear deformation between $N=40$ and $N=42$. The data also indicate the effects of the approaching shell closure at $N=50$.NUCLEAR REACTIONS $^{70,72,74}\mathrm{Ge}$($t$,$p$), ${E}_{t}=17$ MeV $\ensuremath{\sigma}(\ensuremath{\theta})$, DW analysis.

On the correlation between resistivity changes and formation of germanium nuclei in AlGe alloys

The formation of germanium nuclei in a supersaturated AlGe alloy at temperatures below 140 °C has been observed by small angle X-ray scattering and resistivity changes. The latter have been analyzed quantitatively using the X-ray results. The resistivity decreases by (1) trapping of free, quenched-in vacancies by germanium atoms and by (2) reduction of the solute content and the vacancy concentration when nuclei form. Both solute atoms and vacancies are needed to form Ge nuclei since Ge has a larger atomic volume than the Al matrix. Simultaneously, the resistivity is increased proportional to the total interface area of these nuclei. This interpretation leads to reasonable parameters and confirms the internal consistency of the atomic model. Die Keimbildung von Germanium in übersättigten AlGe-Mischkristallen bei Temperaturen unterhalb 140 °C wurde mittels Röntgen-Kleinwinkelstreuung und Widerstandsmessungen untersucht. Die Änderung des Widerstandes wurde mit Hilfe der Ergebnisse aus den Röntgenuntersuchungen analysiert. Danach nimmt der Widerstand ab durch (1) Einfang von freien Leerstellen durch Germanium-Atome und (2) durch Abnahme der Konzentration von Germanium und Leerstellen in der Matrix bei der Keimbildung. Beide Defekttypen werden zur Keimbildung von Germanium benötigt, da das Atomvolumen der Ausscheidung wesentlich größer ist als das der Matrix. Gleichzeitig mit der Widerstandsabnahme (2) tritt eine Erhöhung derselben proportional zur gesamten Oberfläche der Keime auf. Diese Interpretation führt zu vernünftigen Parametern und bestätigt das angenommene Modell.