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1.
Low-lying states in 95Tc were studied with the 93Nb(α, 2nγ)95Tc reaction. The level scheme was obtained from the γ-γ coincidence measurement. The spin assignment was made on the basis of the observed γ-ray angular distributions and the excitation functions. The 337 keV72+, 627 keV (52+), 882 keV132+and 957 keV112+ states, and possibly state, are found to be strong candidates for the core multiplet states [(1g92)p?2+]J. These states are discussed in term of a weak coupling model and the dressed three-quasiparticle model. The observed γ-ray angular distributions are compared with expectations based on a simple deexcitation model of the (α, 2nγ) reaction.  相似文献   

2.
Lifetime and g-factor measurements have been made with pulsed beam-γ time-differential techniques using the 89Y(α, 2n)91Nb and 88Sr(α, n)91Zr reactions. A mean lifetime τ = 14.4 ± 0.5 nsec and a g-factor of 1.26 ± 0.04 were obtained for the 132? 1985 keV level in 91Nb and τ = 41.9 ± 1.2 nsec and g = 0.70 ± 0.01 were obtained for the 152? 2288 keV level in 91Zr. These results are compared to theoretical calculations for g92)2p12) and g92)(πp12)(vd52) configurations in 91Nb and 91Zr, respectively.  相似文献   

3.
High-spin states of the N = 48 nucleus 90Mo have been studied using the 33 MeV 90Zr(3He, 3nγ) reaction. A previously unknown level structure above the 8+ isomer and several new lower-lying levels have been identified. The results are discussed in terms of shell-model calculations which allow four protons in the 2p12and 1g92 subshells and two neutron holes in the 1f52, 2p32, 2p12, or 1g92 orbitals.  相似文献   

4.
Low-lying states in 96Tc excited through the 96Mo(d, 2nγ) reaction have been investigated by means of on-line internal conversion electron and γ-ray spectroscopy. Measured singles spectra and relative excitation functions together with particle-γ and γ-γ coincidences were used to identify and fit the transitions in a level scheme. The low-lying positive-parity states 2+–7+and negative-parity states 2? and 3? are compared with those appearing systematically in doubly odd 94, 98Tc and 92–96Nb isotopes. Comparison is also made with simple shell-model calculations for those nuclei based on the π(p12,g92)pν(d52)n configuration space and the tendency of the multiplet structure of the wave functions is discussed.  相似文献   

5.
The (d, 3He) and (α, t) proton transfer reactions on 91Zr were studied at incident energies of 24.3 and 35.4 MeV, respectively. Angular distributions were measured from 6° to 50° (90Y) and 60° (92Nb). High detection efficiency and good energy resolution were obtained by using a magnetic spectrograph in connection with a multiwire proportional chamber. For the low-lying multiplet levels in both nuclei angular momentum transfers and spectroscopic factors were determined by DWBA analysis. In 92Nb the states at 0, 0.135, 0.29, 0.36 and the sum of the states at 0.48 and 0.50 MeV show typical l = 4 shapes. They belong to the (1g92π)(2d52ν) sextet. The corresponding multiplet in 90Y is weakly populated ( ≦ 20 μb/sr), and l = 4 shapes are found for the levels at 0.68, 0.78, 0.95, 1.05 and 1.30 MeV proving previous assignments. The members of the low-lying (2p12π)(2d52ν) doublets in 90Y and 92Nb exhibit a characteristic l = 1 angular shape. The levels at 1.42, 1.57, 1.64, 1.76 and 1.81 MeV in 90Y are excited both by l = 1 and l = 3 resulting from a strong mixing of the (2p32π)?1(2d52ν) and (1f52π)?1 (2d52ν) multiplets. Only the level at 2.03 MeV displays a pure l = 3 shape. From the spectroscopic information on the (2p12π)(2d52ν) and (1g92π)(2d52ν) multiplets in 90Y and 92Nb the g.s. configuration mixing in 91Zr is deduced.  相似文献   

6.
Excited states in 82Kr have been studied in the reaction 80Se(α, 2n) by using in-beam γ-ray spectroscopy. Measurements of γγ coincidences, excitation functions, angular distributions and the linear polarization of the γ-rays have been carried out. All together, 38 levels have been identified up to I = 12h? and excitation energies up to 6 MeV. For 23 of these levels the mean lifetime could be determined by Doppler shift and the pulsed-beam γ-timing methods. Most of the levels could be grouped into collective bands according to measured B(E2) values. Two sequences, Iπ = 8+, 10+, 12+, are interpreted as rotation-aligned 2q.p. bands built up on g92 protons and neutrons, respectively. Interaction matrix elements between these bands were deduced as V ? 10 keV. Additional states, Iπ = (6+), 7+, 8+, indicate coexistence of rotation-aligned and deformation-aligned 2q.p. excitations. An odd-parity ΔI = 1 band is ascribed to proton excitations of the type g92 ? P32f52. Several fast M1 transitions with B(M1) = 0.1–1 W.u. have been observe states of equal spin. They are interpreted as being due to configuration mixing.  相似文献   

7.
Results from the proton transfer reactions, 143Nd(3He, d) and 143Nd(α, t), and γ-ray studies have been used to characterize the levels in 144Pm. The spins, (3He, d)(α, t) cross section ratios and γ-ray branching ratios for the states below 600 keV can be interpreted consistently in terms of the mixed π2d52ν2f72 and π1g72ν2f72 shell-model configurations. The γ-ray intensity ratios measured in the 141Pr(α, nγ) and 144Nd(p, nγ) reactions exhibit a strong and smooth dependence on level spin. Theoretical calculations employing a residual surface delta interaction are in reasonable agreement with the twelve observed low-lying negative parity states. The eight positive parity states between 841 and 1451 keV are presumed to arise from the π1h112ν2f52 configuration.  相似文献   

8.
The 58Ni(τ, α)57Ni reaction has been studied at 25 MeV incident energy. Angular distributions have been measured from 5° to 50° with a split-pole spectrometer up to 13.5 MeV excitation energy. A local zero-range DWBA analysis has been carried out, allowing l-assignments for about eighty levels, most of them previously unknown. An isospin-dependent potential has been used in the calculation of the neutron form factor for both T<and T> states, and the C2S values deduced using this procedure are compared to those obtained with the usual separation energy method. Analog states of eleven 57Co levels have been identified and the eventuality for isospin mixing in 57Ni has been discussed. A sum rule analysis has been carried out and energy centroids of hole states have been determined. About 60% of the 1d52and 2s12T< strengths and the full 1d32 and 1f72 hole strengths are observed. It is shown that the two excess neutrons in the 58Ni ground state mainly populate the 2p32, 1f52and 2p12 orbitals, whereas the occupancy number of the 1g92 subshell is found to be smaller than 0.1%. Some non-pickup angular distributions have also been observed and a CRC analysis assuming two-step processes in the (τ, α) reaction and weak-coupling wave functions for final states has been attempted. Assignments of Jπ values are proposed for four 57Ni levels, based on this analysis.  相似文献   

9.
The 113, 115In(α, 3nγ)114, 116Sb reactions have been studied using γ-ray spectroscopic techniques. The experiments included γ-ray excitation function, γ-γ coincidence, lifetime, γ-ray angular distribution and conversion electron measurements. A ΔJ = 1 rotational band has been observed in either of the 114, 116Sb final nuclei. Energy spacings and electromagnetic properties of the band show strong resemblances with those of rotational bands in the adjacent odd-mass Sb nuclei. In addition two-quasiparticle and two-quasiparticle core coupled states have been observed in these nuclei. One isomer was identified in 116Sb, i.e. a Jπ = 11+ state at 1889 keV (T12 = 4.0±0.1 ns). A simple model is proposed which explains the ΔJ = 1 band in terms of rotational alignment of the h112 neutron with the deformed rotating odd-A core.  相似文献   

10.
Nuclear states of 82Rb were studied through the 81Br(α, 3n) reaction at various bombarding energies between 30 and 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and γ-time distributions with respect to the beam bursts were determined. Levels at 123.2, 187.7, 233.6, 796.3, 1214.1 keV and tentatively at 1835.5 keV were observed. It was not possible to establish whether the lowest state of the proposed level scheme corresponds to the ground state or to the T12 = 6.2 h isomeric state. The 45.9 and 64.5 keV γ-rays do not exhibit any measurable lifetime and a limit T12 ≦ 5 ns has been determined. The situation is similar for the 123.2 keV γ-ray, although in this case the presence of a long-lived component cannot be ruled out.  相似文献   

11.
The level structure of 117Sb was investigated in the reactions 115In(α, 2nγ)117mSb, 117Sn(d, 2nγ)117mSb and 117Sn(p, nγ)117mSb. In order to confirm level sequences and to assign spins and parities to levels populated in the decay of the isomeric three-particle state T12 = 340 μs), prompt and delayed γ-ray spectra, lifetimes, γ-γ coincidences, γ-ray angular distributions, conversion electrons and excitation functions were measured. The spin 252+ of the isomeric state can be explained by the three-particle configuration [π(d52); v(h112)2 10+]252+. This is supported by the experimentally determined g-factor of g = O.115 ± 0.006. Other levels in 117Sb can be interpreted as particle states coupled to anharmonic vibrations of the core. The existence of an excited 92+[404] quasirotational band is experimentally proved and is supported by calculations of the equilibrium deformation.  相似文献   

12.
The γ-decay of the deeply-bound hole states in 111Sn has been investigated at 32 MeV incident energy by means of the 112Sn(3He, αγ) reaction. The α-particles emitted near 0° were detected in a Si counter located at the image plan of the superconducting solenoidal spectrometer SOLENO. The γ-rays in coincidence with the α-particles were detected by two Ge(Li) detectors located at 90° and 142° with respect to the beam direction, respectively. Energies, spins and decay schemes have been established for the low-lying states up to 2.5 MeV excitation energy in 111Sn. The γ-decay of the broad bump, located around 4.2 MeV and previously attributed to neutron pick-up from the inner 1g92, 2p12, and 2p32 neutron. Subshells, reveals the importance of quasiparticle-phonon m the spreading mechanism of the inner-hole strengths. The 1g92 and 2p strength functions have been deduced from the α-decay of the enhanced structures (3 ≦ Ex≦ 8 MeV). They are compared to the ones measured in previous inclusive neutron pick-up experiments and to those calculated in the framework of the quasiparticle-phonon nuclear model.  相似文献   

13.
Differential cross sections were measured for 46Ti(p, p) and 46Ti(p, p1) at four angles between Ep = 1.5 and 3.1 MeV, with an overall energy resolution of about 300 eV. Spins, parities, total and partial widths were extracted for 144 resonances. Six analogue states were identified. The s-wave states have expected spacing and width distributions, while the p12 states behave anomalously. The s12, p12 and p32 strength functions were determined.  相似文献   

14.
The 6164, 6284, 6310, 6383, 6480, 6777 and 6803 keV states have been studied via the capture reactions 14N(α, γ)18F and 17O(p, γ)18F. These studies yield respective assignments of JπT = 3+(1), 2+(0+1), 3+(0), 2+(0+1), 3+(0), 4+(0) and 1+, 2 or 3+(0). Information on radiative widths, branching and multipole mixing ratios is reported. The 6164 and 6777 keV states are well described theoretically by simple (d52s12)3+and (d52d324+ configurations, respectively. The 2+ states at 6284 and 6383 keV are mixed in isospin. A comparison of the observed properties with the available model calculations is presented for the above states as well as for some low-lying positive-parity states.  相似文献   

15.
The 44Ca(p, γ) reaction was studied for 45 resonances for Ep = 1.6?2.2 MeV. The overall proton energy resolution was 300–350 eV; the γ-rays were detected with both NaI(T1) and Ge(Li) detectors. Partial and total γ-ray widths were measured for each of the fine structure states of the 32? and 12? analogue states at Ep = 1.65 and 2.04 MeV, respectively. The data are examined for correlations between the partial widths (Γp, Γp′, Γγi, Γγtotal) in different channels. The γ-ray intensities are compared with (τ, d) spectroscopic factors.  相似文献   

16.
High resolution γ-ray studies have shown the decay patterns of isomers of 85Y to be very complex. A level scheme of 85Sr is proposed from the results of γ-γ coincidence measurements. Spin and parity assignments to the levels of 85Sr were made on the basis of log ft values, nuclear reaction data and γ-ray branchings. The level scheme is discussed within the theoretical framework of n(g92)?3 cluster properties.  相似文献   

17.
92, 94Nb and 94, 96, 98Tc have been produced by the (p, n) reaction at proton energies on and near the d52 isobaric analog resonance. 95,97Tc have been produced by the (p, γ) reaction below the (p, n) threshold. Internal conversion electrons due to the decay of their excited states were detected on-line with a mini-orange spectrometer which is optimized for the energy range 50 to 500 keV. Gamma rays from these nuclei were detected with a thin Ge(Li) detector. Isomeric-delayed internal conversion electrons and γ-rays were observed, using a nanosecond-pulsed beam. The internal conversion coefficients for 55 transitions in these nuclei have been determined and their multipolarities deduced. The multipolarity of the transitions in these nuclei is predominantly M1. Negative parities have been assigned through use of the d52 isobaric analog resonance enhancements of the population of negative-parity final states. The systematic behavior of the 2?, 3? doublet and of the g92 ? d52 multiplet in these nuclei is discussed.  相似文献   

18.
The high-spin level structures of 152Dy and 153Dy were studied experimentally with 154, 155Gd(α xnγ) in-beam reactions, and for 152Dy also with 144, 146Nd(12C, xnγ) reactions. The experiments included measurements of singles γ-ray and conversion-electron spectra, γ-ray angular distributions and Eγ-t and Eγ-Eγ-t coincidences. A multiplicity filter set-up was used to study the feeding and decay of isomeric states in 152Dy. In 152Dy about twenty so far unknown levels were found, including two high-spin isomeric states with T12 ≈ 60 and ≈ 13 ns at excitation energies Ex ≈ 5.04 and 6.08 MeV, respectively. These states are compared with recent calculations on yrast traps. The level scheme of 153Dy contains 28 levels up to Ex = 4.1 MeV and Jπ = (372+). Band structures in both nuclei are discussed in comparison with other N = 86 and N = 87 isotones.  相似文献   

19.
The decay of 161Yb (T12 = 4.2 min) has been investigated with Ge(Li) and Si(Li) detectors and a toroidal β-spectrometer. Isobarically separated samples produced by the YASNAPP facility at Dubna Institute were used. The singles γ-ray spectrum, the conversion electron spectrum, γ-γ-τ and e-γ coincidences have been measured. In all, 67 γ-ray transitions have been observed. A decay scheme for 161Yb is proposed involving 12 excited states in 161Tm. The 72+[404], 72?[523] and 52+[402] levels have been identified. The interpretation of the high-lying levels is discussed. The Q-value of 161Yb decay has been determined to be 3850 ± 250 keV. The A-dependence of the energies of the one-quasiparticle states in odd-A Tm isotopes is demonstrated.  相似文献   

20.
The reactions 17O(d, t) 16O and 17O(d, τ)16N have been investigated at Ed = 52 MeV. Energy spectra of tritons and τ-particles have been measured simultaneously up to excitation energies of 22 MeV in 16O and 10 MeV in 16N, respectively. Spectroscopic factors have been obtained by a DWBA analysis of the measured angular distributions. From the comparison of the t- and τ-spectra analog (T = 1) states in 16O could be identified and the distribution of T = 0 and T = 1 spectroscopic strengths could be deduced. Nearly the total 1p12 and 1p32 hole strengths have been found and the 1d521p12?1and 1d521p32?1 particle-hole multiplets could be located both for T = 0 and T = 1. The average residual interactions in both shell-model configurations turned out to be strikingly different.  相似文献   

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