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1.
The lifetime of the first excited state in99Sr has been determined by the delayed γ-γ coincidence method. The value of t/2=0.58(9) ns corresponds to a deformation parameter ß=0.38(4). The deduced z> value confirms the previously proposed ν[411]3/2 Nilsson assignment for the99Sr ground state. In addition, lifetime values for the 2+ (t1/2=0.40(8) ns) and 0+ (t1/2=5.36(23) ns) states in100Zr are obtained, which deviate from older measurements and indicate a larger deformation of ß=0.39(4).  相似文献   

2.
We have deduced the linear momentum transferred from the projectile to the fissioning nucleus in the reaction20Ne+197Au at 30 MeV/A by measuring the folding angle between the two fission fragments. We found that the most probable linear momentum transfer represents 76% of the initial value.  相似文献   

3.
The EC/β+-decay of the odd-odd nucleus100Ag was studied by means of total absorptionγ-ray spectrometry. Most of the Gamow-Teller strength was found to be concentrated at an excitation energy of 5.6 MeV in100Pd, the FWHM of this resonance being 1.5 MeV. The measured strength distribution which is interpreted within the BCS approximation as being due to the dominant population of four-quasiparticle excitations, resembles the distribution predicted by an advanced shell-model calculation for the98Ag →98Cd decay.  相似文献   

4.
A new method involving Doppler spectroscopy with laser techniques is proposed to observe bound-state β-decay of tritium. This process, although theoretically expected to occur, has not yet been observed. The proposed method is, in principle, capable of exposing a finite mass of the neutrino. The low source temperatures and laser spectroscopic resolution necessary for a neutrino mass measurement, although extremely difficult to achieve, appear accessible with conceivable advances of these techniques. The underlying discussions and the writing of a first draft of this paper took place in 1982 during an exciting two-week stay of Solly Cohen at AT&T Bell Laboratories. His enthusiasm for fundamental physics and innovative experimentation encouraged discussions on many interesting problems, of which the present subject and paper are representative. This is the last physics paper bearing Solly's name. It is perhaps fitting that, in this work, Solly returned to the subject of bound-state β-decay on which he wrote one of his first papers, thirty years earlier in 1951. We miss Solly as a wise colleague, teacher and friend. Deceased.  相似文献   

5.
A novel method of deducing the deformation of the N=Z nucleus 76Sr is presented. It is based on the comparison of the experimental Gamow-Teller strength distribution B(GT) from its beta decay with the results of quasi-random-phase approximation calculations. This method confirms previous indications of the strong prolate deformation of this nucleus in a totally independent way. The measurement has been carried out with a large total absorption gamma spectrometer, "Lucrecia," newly installed at CERN-ISOLDE.  相似文献   

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The β-decay of a fictional nuclide, Pandemonium, is created numerically using a statistical model. By analyzing its simulated γ-ray spectrum as experimental data, we find that much γ-ray intensity actually remains unobserved under normal experimental conditions. This results - illustrated for the case of 145Gd - casts doubt on many decay schemes determined from such spectra.  相似文献   

8.
The double-beta beta beta(2 nu)-decay rate of 100Mo to the first excited 0(+) state of 100Ru has been measured by a gamma-gamma coincidence technique that uses two HPGe detectors to observe the two gamma rays ( E(gamma 1) = 590.76 keV; E(gamma 2) = 539.53 keV) from the 100Ru nucleus as it deexcites to the ground state via the 0(+)-->2(+)-->0(+) sequence. Unlike all previous beta beta-decay experiments, this technique provides data which have a large signal-to-background ratio. After a 440-day measurement of a 1.05-kg isotopically enriched (98.4%) disk of 100Mo, 22 detected coincidence events (with an estimated background of 2.5 events) yield a half-life of [5.9(+1.7)(-1.1)(stat)+/-0.6(syst)] x 10(20) years.  相似文献   

9.
Active yttrium was separated from 235U fission products and the decay of 94Y, 95Y and 96Y to the levels of 94Zr, 95Zr and 96Zr, respectively, has been studied with the aid of a 17 cm3 Ge(Li) detector. Gamma-ray energies and intensities were accurately determined. In the decay of 94Y four new transitions at 1232.78 ± 0.35, 1324.97 ± 0.35, 1363.48 ± 0.35 and 2467.00 ± 2.75 keV were observed. The data obtained support the level scheme proposed for 94Zr by Knight et al. and that deduced from more recent reaction data. Evidence supporting the location of the 0+ excited state at 1300 keV is presented. Branching ratios are calculated and a modified level scheme for 94Zr is proposed. In the decay of 95Y the energies of 13 γ-rays, previously identified with the decay of this nuclide, have been accurately measured and are presented in a partial level scheme for 95Zr. The data obtained in this work support the level structure deduced from reaction data by Cohen and Chubinsky and by other workers. New γ-transitions at 550.10 ± 0.23, 1723.30 ± 0.90 and 1805.0 ± 1.0 keV were measured in the decay of 96Y.  相似文献   

10.
The spin of the odd nucleus has been determined to be I = 3 from the beta circularly-polarized gamma correlation studies on two prominent beta-gamma cascades: (i) the 1.19 MeV beta group (966 and 908) keV gamma rays and (ii) the 1.76 MeV beta group- 3.38 keV gamma ray. The matrix element ratio X for the 1.76 MeV beta transition has been determined to be X = 0.40±0.10.  相似文献   

11.
Experimental evidence, which suggests a strong proton-neutron interaction giving rise to deformation and influencing the deformation properties of mass 100 nuclei, is reviewed, as is the large variation in the interaction strength for N=59 isotones and for coexisting states of 46≤Z≤54 isotones. Properties of the recently discovered octupole two-phonon multiplet in96Zr are presented, compared to spdf-boson IBM calculations, and consequences of its fragmentation are discussed.  相似文献   

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13.
Effective charges are calculated for protons and neutrons in the region of mass 90. It is found that their magnitudes differ appreciably depending on whether the proton p 1/2 shell is empty or full. The calculated values are compared with values deduced from nuclei with simple configurations, and from a fit to N=50 data. The empirical values are used in shell-model calculations of quadrupole moments of N=50-58 nuclei. Received: 16 February 1998  相似文献   

14.
An improvement of the ion source of the online fission product separator OSTIS allowed us to identify the new isotopes100Rb(50±10 msec),100Sr (170±80 msec) and148Cs(130±40 msec). Half-lives for99Rb(59±4 msec),99Sr(290±40 msec) and147Cs(235±10 msec) were redetermined. All values were obtained by following the activity build-up and decay with β-multiscaling and γ-multispectra measurements.  相似文献   

15.
The beta-decay asymmetry of the free neutron is measured with polarized neutrons and a long solenoidal beta-spectrometer with 4π electron-detection solid angle. The asymmetry parameter corrected for recoil and weak magnetism isA 0=?0.1146±0.0019, implyingg A /g v =1.262±0.005 for the ratio of the axial-vector to the vector weak coupling constants.  相似文献   

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17.
Grain boundary segregation of Y and Zr in -Al2O3 and the atomic structural environment around the Y and Zr atoms have been investigated using high resolution STEM and EXAFS. At dilute concentrations, the Y ions in -Al2O3 grain boundaries, on average, are coordinated by 4 oxygens, at a distance of 2.30 Å, which corresponds nearly to the Y-O bond length in cubic Y2O3, and Zr ions are coordinated by 5 oxygens at a distance of 2.14 Å, which is approximately the same as the average Zr-O bond length in monoclinic ZrO2. However, in the EXAFS radial distribution function, the Y-cation and Zr-cation next nearest neighbor shell cannot be clearly identified. These results suggest that Y and Zr at dilute concentrations in -Al2O3 occupy grain boundary sites with well defined nearest neighbor cation-oxygen bond lengths similar to those in their parent oxides, but with the next nearest neighbor cation-cation distances varying considerably from site to site. Grain growth can cause grain boundaries to become supersaturated by Y. In this case, both the Y-O nearest neighbor coordination number and the ordering of Y with respect to Al ions beyond nearest neighbor O are increased. This Y-Al distance is the same as that expected for the Y-Al distance when Y substitutes for Al while relaxing the Y-O distance to that in Y2O3. This may indicate that as the Y concentration increases, Y begins to occupy near-boundary sites in planes on each side of the geometrical boundary. In these near-boundary planes, the nearest neighbor ordering extends at least to nearest neighbor cations. Nucleation of the YAG phase leads to the depletion of these partially ordered layers.  相似文献   

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20.
A status report is given of the developments in Leuven concerning in-beam polarization of radioactive nuclei. Some properties of the setup are described and first test results are discussed.  相似文献   

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