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1.
In-beam- andn-measurements have for the first time identified excited states in the 72 157 Hf85 nucleus and have established its yrast levels up to 6.5 MeV and I=(51/2). The results of parameter-free 11-particle recoupling calculations in the framework of the shell model for the configurationsh 11 2/8 f 7 2/3 andh 11 2/8 f 7 2/2 h9/2 are in excellent agreement with the observed levels up to 39/2 at 4.758 MeV. A weakly populated 52 ns 29/2+ yrast isomer at 2.876 MeV is assigned as the three-neutron configurationf7/2h9/2i13/2.  相似文献   

2.
The systematics of-decay modes and radiative widths of highly excited states in28Si has been extended by taking-ray spectra on 60 resonances of the27Al(p,) reaction in the range 1097 keVE p 4492 keV (12643 keVE x 15915 keV) and on the24Mg(,) resonances atE =3355, 3431, 4003 keV (E x =12860, 12925, 13 415 keV). The-decay modes of levels in the sub-resonance region (E x =10–12.5 MeV) were studied with both the27 A1(p, ) reaction and the27 A1(d, n) reaction at Ed=4,5,6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengthsS =(2I+1) p / for 52 resonances of the27Al(p, ) reaction with an emphasis on prospective T=1 states.  相似文献   

3.
Low-lying states of theN=50 nucleus87Rb have been investigated in the (, ') reaction measuring- and delayed-rf-coincidences. A half-life ofT 1/2=6(1) ns was obtained for the level at 1578.1 keV. This experimental result confirms the 9/2+ assignment and the proton 1g9/2 single-particle character of this state. Experimental M2 transition strengths in85,87Rb are compared with predictions of the shell model and the particle-core coupling model.This work was partly supported by the Bulgarian National Research Foundation.  相似文献   

4.
The -decay of150La, the heaviest isotope of lanthanum, has been identified by observing -rays from mass separated activities obtained at KUR-ISOL. From the decay curves of 97.0 and 208.7 keV -rays in150Ce and of Ce-K X-ray, the half-life of150La has been determined as 0.51(3) s. This value is in agreement with theoretical predictions from microscopic theory.  相似文献   

5.
This paper presents a study of the rays from the electron capture decay of 3.63d 100Pd. Singles and coincidence measurements provided an accurate determination of-ray intensities and an improved knowledge of the100Rh level scheme. Experimental evidence supports excitation of levels in100Rh at 86-, 136- and 154 keV, not previously reported from the decay of100Pd.On leave from Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires, Argentina  相似文献   

6.
High-spin states in192Pb were populated via the reaction173Yb(24Mg,5n) at a beam energy of 140 MeV, and the resulting-rays were deteced using GAMMASPHERE. A previously observed superdeformed band in192Pb has been confirmed.  相似文献   

7.
TheQ -values of101Rb,101,102Sr and101,102Y have been measured for the first time at the mass separator ISOLDE by means of-coincidence techniques with a plastic scintillation detector telescope and a large Ge(HP)-detector. For some of these nuclei, also new details of their decay schemes could be derived from the measured-decay properties. The experimental results are discussed, as far as the systematics of two-neutron separation energies derived from them is concerned. In addition, the nuclear masses deduced from theseQ -values are compared with the predictions of recent mass calculations.Dedicated to Prof. Dr. Peter Armbruster on the occasion of his 60th birthday  相似文献   

8.
The -radiation following single and double neutron capture in isotopically enriched62Ni was studied at the high flux reactor of the Institut Laue-Langevin, using a pair and Compton suppressed germanium detector. Measurements before and after 170 d of breeding were performed. The -ray fluxes through63Ni and64Ni are discussed; several new levels and spin-parity assignments were found. On the basis of the known discrete levels and the low-energy neutron resonances, level density parameters were determined within the Constant Temperature Fermi Gas model. The neutron binding energies were measured asB n (63Ni)=6837.92(18) keV andB n (64Ni)=9657.64(24) keV. The63Ni (n, ) cross section for reactor neutrons was measured to be =20 –2 +5 b.Supported by Deutsches BMFT under contract 06 GÖ 141  相似文献   

9.
The decay of101Zr has been investigated at the fission-product separators JOSEF and LOHENGRIN. The half-life of101Zr has been determined to 2.5(1) s and a level scheme for101Nb has been established from ray singles as well as X/3- and — coincidence measurements. Conversion coefficients for transitions in101Nb and level half-lives between 10 ps and 2 ns have been determined. Three rotational bands are identified among the low-lying levels with band heads at 0 keV, 206 keV and 208 keV. The bands are probably based on the Nilsson configurations [422 5/2+], [301 3/2] and [303 5/2], respectively. The deformation has been determined to q=0.40(4) and 0.41(8) for the ground state band and the band based on the 206 keV level from the half-lives of the first and second excited members of these bands. This shows that the rapid onset of deformation at N=60 which is typical for the A=100 region of neutron-rich nuclei, takes also place in the Nb isotopes. Nilsson model calculations describe the experimental data well, especially the several determined transition probabilities including those for E1 transitions from the 206 and 208 keV band heads to the ground state.Dedicated to Prof. Dr. P. Armbruster on the occasion of his 60th birthday  相似文献   

10.
For the first time, detailed decay-spectroscopic investigations were performed for the very neutron-deficientN=50 nuclide98Cd. The98Cd activity was produced in spallation reactions between 600 MeV protons and a natural tin target, yielding a98Cd beam intensity of 10 to 60 atoms/s at the collector of the ISOLDE massseparator. By means of-ray and conversion-electron spectroscopy, 19 transitions were found to follow the +/EC decay98Cd98Ag. The transitions at 61 and 107 keV were shown to beM1(+E2) andE2, respectively, and the98Cd half-life was measured as 9.2±0.3 s. TheQ EC value of98Cd is determined semiempirically and is compared to model predictions together with the measuredQ EC values of the neighbouring cadmium isotopes100,102Cd and theN=50 isotones92Mo,94Ru, and96Pd, taken from the literature. The newly established decay scheme of98Cd includes 9 excited states of98Ag. Four states at 1691, 1861, 2164, and 2544 keV are directly fed by 0+ 1+ Gamow-Teller beta transitions with a summed strength of 3.5 –0.7 +0.8 . This value corresponds to 25±5% of the strength predicted for the GT transformation of a g9/2 proton (in98Cd) into a g7/2 neutron (in98Ag) by the extreme single-particle shell model. The GT-strength splitting and quenching, observed for98Cd, are compared with the corresponding data for lighter even-even N=50 isotones, and are discussed with reference to the predictions of more sophisticated nuclear models. We find that only in some cases it is possible to explain qualitatively the observed GT strength distribution and its total magnitude without renormalizing the free-neutron value of the axial-vector coupling constant.Dedicated to Prof. P. Armbruster on the occasion of his 60th birthday  相似文献   

11.
The gamma-ray spectra emitted after thermal neutron capture in highly enriched50V andnatV targets have been studied using in-pile targets at the ILL high flux reactor and pair and germanium detectors. The neutron binding energies in51V and52V were determined to beB n (51V)=11051.11(17) keV andB n (52V)=7311.22(26) keV. The thermal neutron capture cross-section in50V was measured to be 21 –2 +4 b. From 724 lines attributed to51V, 330 transitions, comprising 90% of the-ray flux, were placed into the level scheme. Fifty-nine primary dipole transitions from the 11/2+ or 13/2+ capture states in51V were established from which the E1 strength distribution was deduced. The energy scaling of these primary transitions was found to follow the E1-giant dipole resonance dominance. Many new levels were established; a number of states proposed in previous (d,p) and (n,) work were confirmed from their primary population and decaying secondary radiations. The density of levels in the high spin (9/2I15/2) region was parametrized with the Fermi gas model. The spin distributions of51V were analyzed and a spin cut-off parameter =2.8 (3) was deduced. — A nearly complete level scheme of52V up to 3.5 MeV excitation and similar results concerning the level density and the primary -ray spectrum were obtained in the51V (n, )52V study.Supported by Deutsches BMFT under contract 06GÖ141  相似文献   

12.
A ridge has been found in a - coincidence matrix obtained from the reaction122Sn(27Al,5n)144Euat 142 MeV.The half-width of the valley is 59 keV,which is similar to the energy spacings in the superdeformed bands in 143Euand 142Sm.This indicates the existence of superdeformed bands in 144Eu.This work was supported by the Natural Sciences and Engineering Research Council of Canada and AECL Research. We thank the crew and staff at TASCC for supplying the beams, and Dr.R.A.Wyss for use of the CSM and TRS codes.  相似文献   

13.
A mini transmission-ray Compton polarimeter was developed for the measurement of the sign of magnetic moments of radioactive nuclei with low-temperature nuclear orientation. The signs of the magnetic moments of the following isotopes were determined:193Os [=+0.7297(16) N];191m Ir [=+6.20(9) N];192Ir [=+1.924(10) N];194Ir [=+0.39(1) N];195m Pt [=–0.605(15) N].Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday  相似文献   

14.
he so far unknown nucleus147Er has been identified by means of - recoil and — coincidences through the reaction92Mo(58Ni,2pn) at a bombarding energy of 260 MeV. The level scheme has been obtained up to 5.0 MeV of excitation energy and shows collective excitations built on the h11/2 intruder orbital.  相似文献   

15.
Beta-coincident-rays were measured from implanted44V and42Sc nuclei. These were selected after58Ni+nickel reactions by means of the LISE3 spectrometer at GANIL. The production of the isomeric states was identified by detecting their typical-delayed-ray cascades. From the intensities of the detected-lines the ratio between isomer and ground-state production of44V follows to be 1 to 3.0(4).on leave of absence from GSI Darmstadt.  相似文献   

16.
The half-lives of seven levels in105Mo have been determined with high precision at the fission-product separator Josef. The-- triple coincidence method with plastic and BaF2 scintillators was used for a determination of the time between the q feeding of a level of interest and its depopulation. A value of q =0.38 (1) for the deformation parameter has been deduced from the half-lives of the first and second excited states. The results of Particle-Rotor model-calculations with the Nilsson parameters=0.084 and=0.28 support the assignment of the Nilsson orbital [532] 5/2 to the ground state of105Mo.The authors acknowledge with pleasure fruitful discussions with Profs. W.R. Phillips, I. Ragnarsson and O.W.B. Schult.  相似文献   

17.
We have measured the asymmetry coefficientsA of the circularly polarized--angular correlations for the allowed-transitions in21F and39Cl. Thus, it was possible to estimate the isospin-forbidden Fermi matrix elements ¦MF¦forb.A mixing ratio E3/M2= –0.20±0.04 was obtained for the 1.52 MeV -transition in39A. We also discuss the possibility of a charge-dependent analog-antianalog interaction in the21 Ne nucleus.  相似文献   

18.
The emission of high-energy-rays in the deexcitation of hot40Ca and39K nuclei formed in heavy-ion fusion reactions at excitation energyE x 90 MeV has been studied. The high energy-rays were measured in coincidence with evaporation residues or light charged particles. The spectrum from the self-conjugated compound nucleus40Ca shows an appreciable yield suppression in the Giant Dipole Resonance (GDR) energy region with respect to the39K, due to isospin selection rules in the dipole-decay. The spectral line shapes of the spectra are well reproduced by using a statistical code which treats explicitly the isospin quantum number in evaluating level densities and transmission coefficients. The GDR parameters determined from the present coincidence measurements are in good agreement with the systematic in theA 40 mass region at lower bombarding energy based on the analysis of inclusive spectra.We thank M. Caldogno for technical support in the development of evaporation residues detectors. We acknowledge the participation of M. Anghinolfi, P. Corvisiero, M. Taiuti and A. Zucchiatti in the early stages of this work. Thanks are due to M. Kicinska-Habior for providing the isospin-dependent code. Discussions with B. Fornal are also gratefully acknowledged.  相似文献   

19.
The particle- angular correlation of the 2+0+ transition in148Nd, Coulomb excited by90Zr projectiles, was investigated to search for a transient electric field gradient expected to be present during the stopping of the recoils in208Pb. An upper limit of Vzz <>19V/cm2 was obtained for148Nd recoiling with initial velocities of 0.05 c.  相似文献   

20.
Collective properties of206,208Pb have been investigated with gamma-ray spectroscopy using nuclear and electromagnetic excitation by208Pb projectiles. From the measurement of particle-particle- and particle-particle- coincidences a new energy level in208Pb at 5.683 MeV was observed and the data suggest an interpretation as a 2-phonon octupole vibrational state with spin 4+ or 6+. For this state one finds the same dynamical deformation parameter 3 as for the first-excited collective 3 state. The results are compared to predictions of models which consider, in particular, the aspects of the quadrupole interaction and the interaction of the 2-particle pairing vibration with the 2-phonon octupole vibration. For the206Pb+208Pb system at 6.2 MeV/u the nuclear potential could be determined from the measured inelastic cross sections.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday  相似文献   

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