Structure of 74Ge from the 72Ge(t,p) reaction

The reaction ⁷²Ge(t, p)⁷⁴Ge has been investigated with a 15 MeV triton beam. Fifty energy levels of ⁷⁴Ge were identified up to about 4.9 MeV excitation, eighteen of which were previously unreported. Angular distributions were measured and compared with DWBA calculations. Two low-lying states at 1.913 and 2.164 MeV have been assigned as J^π = 0⁺, corresponding to the 0₃⁺ and 0₄⁺ states in ⁷⁴Ge. The 4₂⁺ state has been located at 2.674 MeV, and the 2₄⁺ at 2.836 MeV. Many additional spin and parity assignments have been made. The ⁷⁴Ge nucleus shows a considerably different structure of 0⁺ states compared with the neighboring ⁷⁶Ge and ⁷⁸Ge nuclei, perhaps further evidence for the shape transition suggested recently for the Ge isotopes.     

Levels in74As from the74Ge(p,nγe)74As reaction

The low-lying levels in⁷⁴As have been studied by means ofγ-ray and internal conversion electron spectroscopy following the⁷⁴Ge(p,n)⁷⁴As reaction. New levels at 372.7, 532.8, 632.1, 731.6, 752.7, 758.3, 801.6, 902.9 and 1128.5 keV, not observed in earlier studies, have been established.J ^π assignments have been made to several low-lying levels. An earlier ambiguity regarding the identification of an isomeric level has been clarified. The half-life of a level at 271.4 keV has been measured to be 1.0±0.1 nsec; in addition, limits on half-lives of levels at 182.7, 277.5 and 425.4 keV have been assigned. The level structure is discussed on the basis of available nuclear models.     

Influence of the entrance channel in the fusion reaction 318 MeV 74Ge+74Ge

Entrance channel effects in the fusion of heavy ions have been studied by using the ⁷⁴Ge+⁷⁴Ge reaction at 318 MeV. The population of the yrast superdeformed band in ¹⁴⁴Gd shows an increase when compared with the results obtained in the more asymmetric ⁴⁸Ti+¹⁰⁰Mo reaction at 215 MeV. The relative yields of the different evaporation residues produced in the ⁷⁴Ge+⁷⁴Ge and in the ⁴⁸Ti+¹⁰⁰Mo reactions are very similar, with the exception of the ^145,144Gd residual nuclei (3n and 4n decay channels) which are populated with a larger yield in the symmetric reaction. Statistical model calculations reproduce qualitatively such effect if a fission delay is explicitly taken into account. Effects related to fusion barrier fluctuations seem to be important in determining the spin distributions of the compound nucleus. The spectra of the high energy γ-rays emitted in the ⁷⁴Ge+⁷⁴Ge reaction have been measured as a function of the γ-ray multiplicity as well as in coincidence with selected evaporation residues. They are reproduced by standard statistical model calculations with GDR parameters taken from systematics, demonstrating that, in agreement with dynamical model prediction, the emission of γ-rays from the dinucleus formed in the earlier stage of the collision is unimportant.     

Beiträge zu den Niveauschemata der Ge-Isotope71Ge,73Ge,74Ge und75Ge aus der Untersuchung von (n, γ)-Reaktionen in natürlichem Germanium

Low energy γ-spectra from neutron capture in natural germanium have been studied with several high resolution Ge(Li)-detectors. Measurements have been made with two different target configurations. In the first measurement a normal Ge-target was irradiated with neutrons; no neutrons were allowed to enter the Ge(Li)-detector. In the second measurement the Ge(Li)-detector was used simultaneously as target and as γ- ande ^?-detector. By combination of the results convertion coefficients of several transitions in⁷³Ge have been determined. Several unknown low energy transitions in Ge isotopes have been found with the aid of the second method. The level schemes of⁷¹Ge,⁷³Ge,⁷⁴Ge and⁷⁵Ge have been revised by means of coincidence measurements with a Ge(Li)-Ge(Li)-coincidence system of high efficiency and resolution.     

High spin states in77Se populated by the74Ge(α,n γ) reaction

⁷⁷Se has been investigated by the reaction⁷⁴Ge(α,nγ) at 14 MeV. Gamma singles spectra, gamma angular distributions and gamma-gamma coincidences have been taken. A level scheme has been established, spins and parities have been assigned. States of a rotational band on the 1/2^? ground state, a rotational band on the 5/2^? 249.7 keV state and an anormal band have been identified. Nuclear Reaction ⁷⁴Ge(α,n γ)E _α=14 MeV; measuredE _γ ,I _γ ,γ-γ-Coin.,γ-ang. distr.⁷⁷Se deduced levels,J, π. Enriched target, Ge (Li).     

Study of elastic and inelastic scattering of protons from 74Ge at isobaric analogue resonances

Excitation functions of the elastic and the inelastic proton scattering leading to the ground state and to the 2⁺ (0.596 MeV) state in ⁷⁴Ge were measured at 90°, 125°, 140° and 165° at bombarding energies from 3.34 to 5.4 MeV. Ten isobaric analogue resonances in ⁷⁵As were identified. Five of these resonances decay to the 2⁺ excited state in ⁷⁴Ge. Angular distributions of the inelastically scattered protons were measured at bombarding energies corresponding to these resonances. The partial widths of the isobaric analogue states for decay to the ground state and to the 2⁺ excited state in ⁷⁴Ge were determined as well as the l-values of the captured protons and the spins of the resonances. The Coulomb displacement energy for the pair ⁷⁵As-⁷⁵Ge was found to be 10.01 MeV. A comparison is made with the parent analogue states in ⁷⁵Ge. The results indicate that several levels of ⁷⁵Ge may be described as having a large component of a single particle state coupled to the first 2⁺ excited state in ⁷⁴Ge, and that the 2⁺ state has a configuration with a large 2p-2h component.     

Prompt <Emphasis Type="Italic">γ</Emphasis> rays in <Superscript>77</Superscript>Ge and <Superscript>75</Superscript>Ge after thermal neutron capture

The reactions ⁷⁴Ge(n, γ) and ⁷⁶Ge(n, γ) have been measured with cold neutrons generated by the research reactor FRM II near Munich, Germany. The γ rays have been detected by two Compton-suppressed HPGe systems in single and coincidence mode. The number of identified prompt transitions and levels in ⁷⁷Ge was increased significantly and the decay scheme could be reconstructed for the first time. The decay scheme was also reconstructed for 68 prompt transitions in ⁷⁵Ge. Previously reported inconsistencies of the γ-ray intensities in the ⁷⁷Ge β decay could be resolved. In particular, the region around 2039 keV was investigated carefully, since the background to the neutrinoless double-beta decay of ⁷⁶Ge must be understood well for the upcoming Gerda and Majorana experiments.     

Study of 74As by the 73Ge(3He,d) reaction

The energy levels of ⁷⁴As have been studied using the ⁷³Ge(³He, d)⁷⁴As reaction at an incident energy of 17 MeV. The overall energy resolution was 30 keV. Twenty-five levels in ⁷⁴As were identified up to 2.2 MeV excitation energy and angular distributions were measured in the interval $\text{3}\text{3}\text{4}\text{°}$ to $\text{86}\text{1}\text{4}\text{°}$. Spectroscopic strengths and l_p values have been extracted for many of the transitions by means of a distorted-wave analysis of the differential cross sections. A comparison with the ⁷⁵As(p, d) data suggests the presence of several unresolved doublets in ⁷⁴As.     

70Ge(α, γ)74Se cross section measurements at energies of astrophysical interest

The cross section of the reaction ⁷⁰Ge(α, γ)⁷⁴Se has been measured over the bombarding energy range of 5.05 MeVα<7.80 MeV using single and coincidence gamma spectroscopy techniques. The experimental S-factor values are in agreement with theoretical statistical-model calculations. Reaction rates for the ⁷⁰Ge(α, γ)⁷⁴Se and the inverse (γ, α) reactions have been determined for appropriate temperatures.     

Neutron interactions with germanium isotopes and amorphous and crystalline GeO2

Coherent neutron scattering lengths and total cross sections have been measured on elemental and oxide samples of ordinary Ge and of isotopically enriched substances. From the experimental results the following values were obtained:

the coherent scattering lengths (in fm) of the bound atoms Ge(8.185±0.020);⁷⁰Ge(10.0±0.1);⁷²Ge(8.51±0.10);⁷³Ge(5.02±0.04);⁷⁴Ge(7.58±0.10) and⁷⁶Ge(8.2 ±1.5);

the absorption cross sections at 0.0253 eV (in barn) for Ge(2.20±0.04);⁷⁰Ge(2.9±0.2);⁷²Ge(0.8±0.2);⁷³Ge(14.4±0.4) and⁷⁴Ge(0.4±0.2);

the free cross sections for epithermal neutrons and the zero energy scattering cross sections.

On the basis of this data, the isotopic- and spin-incoherent cross sections and thes-wave resonance contributions to the coherent scattering lengths have been determined and discussed. Transmission measurements at 0.57 meV on amorphous and crystalline GeO₂ yielded for the amorphous sample an inelastic cross section eight times larger than for the crystalline samples. This effect corresponds to a clearly higher density of low energy states in the amorphous than in the crystalline substances.     

Mass and excited levels of the neutron-rich nuclei 73Zn and 74Zn studied with the 76Ge(14C, 17O) and (14C, 16O) reactions

The ⁷⁶Ge(¹⁴C, ^{16, 17}O)^{74, 73}Zn reactions have been studied at 72 MeV bombarding energy. The mass excesses of ⁷³Zn and ⁷⁴Zn were determined to be ?65.41 ± 0.04 and ?65.62 ± 0.04 MeV, respectively. In addition, previously unknown excited levels were identified in both nuclei. The structure of ⁷³Zn is discussed in terms of HFB calculations.     

70Ge(α, γ)74Se cross section measurements at energies of astrophysical interest

The cross section of the reaction⁷⁰Ge(α, γ)⁷⁴Se has been measured over the bombarding energy range of 5.05 MeV <E _α < 7.80 MeV using single and coincidence gamma spectroscopy techniques. The experimental S-factor values are in agreement with theoretical statistical-model calculations. Reaction rates for the⁷⁰Ge(α, γ)⁷⁴Se and the inverse (γ, α) reactions have been determined for appropriate temperatures.     

The Raman spectroscopy of neutron transmutation doping isotope Germanium nanocrystals embedded in SiO2 matrix

We have succeeded in doping arsenic (As) impurities into isotope germanium nanocrystals (nc-⁷⁴Ge) uniformly dispersed in a SiO₂ matrix by using the neutron transmutation doping (NTD) method. The samples’ inner structural transmutation is studied by combining Raman scattering, X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscope (TEM) methods. The Raman spectrum of the doped sample exhibits a relative intensity increase of the low frequency tail, blue shift of the main Raman peak (∼300 cm⁻¹) and a high frequency tail, while the undoped sample does not. Together with the XRF, XPS and TEM, we believe that the relative intensity increase of the low frequency tail arises from an increase of amorphous ⁷⁴Ge (a-⁷⁴Ge) induced by the irradiation damage. The blue shift of the main Raman peak comes from the mismatch of the crystal lattice which arose from the As impurity introduction. And the high frequency tail is due to transmuted-impurities (As) in the nc-⁷⁴Ge which was introduced by NTD.     

States of 76Ge via (p,p′) inelastic scattering at 22 MeV

The ⁷⁶Ge(p, p′) inelastic scattering has been studied at 22 MeV with an overall resolution of 10 keV using a tandem Van de Graaff and a split-pole magnetic spectrometer. Angular distributions have been obtained for about 40 levels in ⁷⁶Ge. Vibrational and asymmetric rotor model CC calculations and DWBA calculations have been made. Spin and parity assignments have been deduced.     

Effect of As doping on the photoluminescence of nanocrystalline Ge embedded in SiO2 matrix

Samples of nanocrystalline ⁷⁴Ge embedded in amorphous SiO₂ film were prepared by ⁷⁴Ge ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor then the second annealing followed. Irradiation with thermal neutrons leads to doping of nanocrystalline ⁷⁴Ge with As impurities due to nuclear transmutation of isotope ⁷⁴Ge into ⁷⁵As. Transmission electron microscope, X-ray fluorescence, X-ray photoelectron spectroscopy, laser Raman scattering and photoluminescence of the obtained samples were measured. It was observed that with the increase in As-donors concentration, photoluminescence intensity first increased but then significantly decreased. An explanatory model of this non-monotonic behavior was discussed.     

The M2 radiative widths of nuclear levels at about 7 MeV excitation

The M2 widths and M2/E1 mixing ratios in transitions of the form 1⁻¹ → 2⁺ from nuclear levels at about 7 MeV excitation in ⁷⁴Ge, ¹⁰⁰Mo, ¹¹²Cd and ¹⁸⁶W have been measured. The M2 widths are found to be about the same average magnitude as the M2 widths in nuclei with A < 40.     

Isobaric analogue resonances in71As through proton elastic scattering on70Ge

The analogues of the low-lying levels in⁷¹Ge have been observed as resonances in the compound nucleus⁷¹As through proton elastic scattering on⁷⁰Ge in the energy rangeE _p=3.5 to 5.3 MeV. The excitation functions cover the analogue resonances corresponding to states upto 2.3 MeV excitation in⁷¹Ge. The sub-structures in the 5.06 MeV resonance, first observed by Temmer and co-workers have been confirmed in the present experiment. The present investigation reveals similar sub-structures in the 4.13 MeV resonance lending further support to the existence of intermediate structure near an isobaric analogue resonance. The resonance parameters and the spectroscopic factors (for the corresponding parent states) have been extracted. The results are compared with the information available from the⁷⁰Ge(d, p)⁷¹Ge reaction.     

Ab initio determination of crystal lattice constants and thermal expansion for germanium isotopes

The temperature dependence of the equilibrium lattice constants for five isotopically pure Ge crystals (⁷⁰Ge, ⁷²Ge, ⁷³Ge, ⁷⁴Ge and ⁷⁶Ge) and naturally occurring Ge were calculated from ab initio electronic theory within the quasiharmonic approximation. It is shown that at very low temperature, calculations including zero point motions contribution to the free energy correctly reproduced the experimental unit cell parameters for the five isotopes. For ⁷⁰Ge, ⁷⁴Ge, ⁷⁶Ge and naturally occurring Ge, the predicted thermal expansion coefficients agree very well with experiments. The calculated thermal expansitivity for ⁷³Ge does not agree well with experiment. It is speculated that this anomaly may due to the non-zero nuclear spin of the ⁷³Ge isotope.     

Low-lying 134Cs excited states from the (n, γ) reaction

Low-energy γ-ray and conversion electron spectra from the ¹³³Cs(n,γ)¹³⁴Cs reaction have been investigated with a bent cyrstal spectrometer, β-speetrometer, Ge(Li) and Si(Li) detectors. Gamma-gamma coincidence measurements were made with the Ge(Li)-Ge(Li) arrangement. Gamma-gamma delayed coincidences have been studied with the use of the Ge(Li)-NaI(Tl) coincidence set-up. The decay of 2.9 h ^134mCs has been investigated with the prism β-spectrometer and Ge(Li) detector. The half-lives of the 176.403 and 257.112 keV levels have been measured to be 49.7 ± 0.8ns and 12.3 ± 1.1 ns respectively. The neutron binding energy B_n have been calculated to be 6891.4 ± 1.3 keV. Spin and parity assignments have been made for almost all the levels. The possible structure of the levels deduced is discussed.     

Isospin components of the giant dipole resonance in several germanium isotopes

Measurements of the (γ, np) cross sections of ⁷⁰Ge, ⁷²Ge, ⁷⁴Ge and ⁷⁶Ge and the (γ, p) cross section of ⁷⁴Ge are reported. The (γ, np) reaction is discussed as a channel for the observation of the T = T₀ + 1 component of the giant dipole resonance of the nuclear photo effect, and experimental evidence is presented in support of this conjecture in Ge isotopes.