Energy available for the double beta-decay of 76Ge

The Manitoba II high-resolution mass spectrometer has been used to determine the atomic mass difference ${}^{76}\text{Ge}\text{?}{}^{76}\text{Se}\text{= 2040.71 ± 0.52}\text{keV}$. This result, which is superior in precision and accuracy to previous values, should facilitate current searches for the neutrinoless double beta-decay of ⁷⁶Ge.     

New levels and transitions in ^72Ge following thedecay of ^72Ga

The decay of ^72Ga has been investigated by means of γ-ray spectroscopy. The 72Ga nuclei were produced through the ^71Ga(n, γ)^72Ga reaction. The Compton-suppressed spectrometer and high-purity Ge detectors have been used singly and in coincidence, separately, to study γ-rays in the β-decay of ^72Ga to ^72Ge. Ninety-three events of γ-rays were reported, of which 7 were observed for the first time. A decay scheme of ^72Ga including 4 new levels is proposed which accommodates 87 of these transitions. Spins and parities for new levels are proposed from calculated logft values, modes on the observed decay, and some nuclear reaction experimental results.     

Gamma-spectroscopic investigations on 67Ge

By γ-γ coincidence measurements following the ⁵⁷Fe(¹²C, 2nγ) reaction at E_12C = 40 MeV several new states above 1.5 MeV excitation energy in ⁶⁷Ge have been established. Spin and parity assignments on the basis of the angular distribution, linear polarization and γ-ray yield function indicate very similar structures in ^{67, 69}Ge. The positive-parity states can be followed up to the $\text{17}\text{2}{}^{\mathrm{+}}$ state at E_x = 3.07 MeV followed by a sequence of negative-parity high-spin states at nearly the same excitation energy relative to the $\text{9}\text{2}{}^{\mathrm{+}}$ single-particle state as in the neighbouring nucleus ⁶⁹Ge where these states were found to have strong single-particle admixtures. A reinvestigation of the spin of the E_x = 2.75 MeV level in ⁶⁹Ge resulting in a change of its spin from $\text{15}\text{2}{}^{\mathrm{+}}\text{to}\text{17}\text{2}{}^{\mathrm{+}}$ and for all spins above, removed the discrepancy concerning the spin assignments of corresponding levels in ^{67, 69}Ge. The excitation pattern of the Ge isotopes with 34 ≦ N ≦ 39 clearly indicate same structures probably due to the strong competition between collective and single-particle excitations along the whole chain similar to the results for the Zn isotopes.     

Energy levels of 71Ge from 71Ga(p,nγ)71Ge

Energy levels of ⁷¹Ge were populated by the ⁷¹Ga(p, n) reaction at proton energies between 1.72 and 2.96 MeV and their decay studied by both γ-γ and γ-n coincidences. Spins were determined within the framework of the statistical theory from angular distributions of de-excitation γ-rays and from excitation strengths of levels derived from γ-ray intensities and branching. A level and decay scheme for ⁷¹Ge up to an excitation of 1.3 MeV is presented.     

The beta decay of 137Cs

Evidence is presented to support the view that the approximate shape factor $\text{C = q}{}^2\text{+}\text{b}\text{?}\text{p}{}^2$ does not adequately describe the second-forbidden beta decay of ¹³⁷Cs. An improved formula is given, with single-particle estimates of the nuclear matrix-element ratios. According to this model the coefficient of p² involves considerable cancellation between matrix elements; when due allowance is made for this, good fits to the experimental data are obtained, leading to better estimates of the decay scheme parameters.     

70As(β++EC)衰变到70Ge的低自旋激发态(英文)

通过70As的放射性衰变研究了70Ge的激发态,新发现能量为1 036.99,1 196.66,1 539.29和2 531.7 keV的四条新γ射线,重新确认了2 219.34 keV γ射线的跃迁位置,新确认496.74,1 295.24和1 417.24 keV这三条γ射线首次放入衰变纲图,本工作证实了1 881.67,2 325.42和2 424.41 keV γ射线的跃迁位置,建议了能量为4 243.10和5 265.81 keV的两个新能级,建立了新的衰变纲图,基于比较半衰期和γ跃迁分支比建议了一些能级的自旋-宇称。The excited states of the 70Ge nucleus are investigated in radioactive decay of the 70As. Four new transitions with 1 036.99, 1 196.66, 1 539.29 and 2 531.7 keV are found for the first time. The position of 2 219.34 keV transition are reassigned, the transition positions of 496.74, 1 295.24 and 1 417.24 keV γ-rays are assigned for the first time, and the placements of 1 881.67, 2 325.42 and 2 424.41 keV γ-rays are confirmed in the present work. Two new levels, at 4 243.10 and 5 265.81 keV excitation energy, respectively, are proposed. The decay scheme is established and for a number of levels spin-parity assignments are suggested on the basis of logft values and γ-branching ratios.     

Mass excesses of 79As, 81As,and 80Ge

Accurate mass measurements for the nuclides ⁷⁹As, ⁸¹As, and ⁸⁰Ge have been measured. Good agreement has been found for ⁷⁹As and ⁸¹As with the Garvey-Kelson transverse mass relation and with several mass model predictions. The agreement for ⁸⁰Ge is not as satisfactory and presents a challenge for understanding mass values far off the line of stability.     

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.     

Nuclear structure study of states in 72Ge and 74Ge with (p,t) reactions

^{74, 76}Ge(p, t) measurements at E_p = 35.4 MeV are reported. It is found that, except for a depression of the ⁷²Ge ground-state energy accompanying the occurrence of a low-lying 0⁺ excited state, the energy level structure of ⁷²Ge is nearly identical to that of ⁷⁴Ge. Dependence of angular distribution shapes at low angles on the transferred neutron configuration is observed, both experimentally and in the DWBA calculations.     

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.     

Decay studies of neutron-rich products from 76Ge induced multinucleon transfer reactions including the new isotopes 62Mn, 63Fe and 71, 72, 73Cu

By irradiating a ^natW target with 9 MeV/u ⁷⁶Ge ions, neutron-rich isotopes in the chromiumgermanium region were produced. On-line mass-separated samples were investigated. The new isotopes ⁶²Mn, ⁷¹Cu, ⁷²Cu and ⁷³Cu were identified and their half-lives measured to be 0.88(15), 19.5(16), 6.6(1) and 3.9(3) s, respectively. The half-life of ⁶³Fe, a nucleus which has previously been detected using particle-identification techniques, was measured to be 4.9(5) s. Decay schemes were derived in most cases. Additional spectroscopic information was obtained on the decays of ⁷³Zn and ⁷⁴Zn. We give evidence that the earlier reported γ-ray activity attributed to ⁶⁷Ni belongs to the decay of the ⁷⁰Cu isomers. At A = 67 we observed a new β-ray activity of 21(1) s half-life which is here assigned to the decay of ⁶⁷Ni.     

Origin of the high-and low-frequency K-satellites of 31Ga, 32Ge and 33As

The origin of the high- and low-frequency K-satellites of ³¹Ga, ³²Ge, ³³ As is explain on the basis of Hayasi's theory of quasi-stationary states. It is shown that the same QSS difference gives rise to a particular satellite of either type in all the elements. The results are compared with those of multiple ionisation theory.     

Nuclear structure relevant to neutrinoless double beta decay: 76Ge and 76Se

The possibility of observing neutrinoless double beta decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of 76Ge (a candidate for such decay) and 76Se (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit.     

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.     

Determination of the (76)Ge double beta decay Q value

The Q value of the (76)Ge double beta decay has been determined by measuring the masses of (76)Ge and (76)Se in a Penning trap using neon- and fluorinelike ions. The obtained masses are 75.921 402 758(96) u and 75.919 213 795(81) u, respectively. The systematic errors of these two determinations are nearly equal, and therefore, the remaining systematic uncertainty of the Q value is drastically reduced. A Q value of 2 039.006(50) keV was obtained improving the accuracy of the accepted value by a factor of 6.     

The half-life for the superallowed fermi beta decay 50Mn(β+)50Cr

The half-life for the decay ⁵⁰Mn(β⁺)⁵⁰Cr has been measured to be 282.8 ± 0.3 ms. This result is ≈ 1% lower than the accepted value. It would bring the ft value for ⁵⁰Mn decay into agreement with recent measurements for other superallowed Fermi decays.     

New limits on fundamental weak-interaction parameters from superallowed beta decay

A new survey of all world data on superallowed beta decays provides demanding tests of, and tight constraints on, the weak interaction. In confirmation of the conserved vector current hypothesis, the vector coupling constant G(V) is demonstrated to be constant to better than three parts in 10(4), and any induced scalar current is limited to f(S)相似文献   

The β− decay of 102Mo

The ¹⁰²Mo activity was obtained by photofission of natural U and thermal-neutron induced fission of ²³⁵U, with subsequent chemical separation of the molybdenum fraction. In addition, nuclei with mass 102 were separated from fission products of ²³⁵U(n_th, f) using the mass separator LOHENGRIN. A decay scheme and absolute γ-intensities are deduced from measured γ-ray, X-ray and γ-coincidence spectra. Logftvalues are calculated. Shell-model calculations for a $\text{(πlg}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^3$$\text{(νlg}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^3$ multiplet have been carried out using effective nucleon-nucleon interactions. The γ-decay between low-lying, low-spin members of this multiplet was studied in detail and compared with the experimental data.