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1.
The depopulation of isomeric states in 176Lu and 182Ta was studied in the (n, γ) reaction by means of delayed γ-γ coincidence measurements with NaI(Tl) and Ge(Li) detectors. The following half-lives, unknown so far, have been obtained for 176Lu: , and ; and for 182Ta: , and . The existence of the isomeric level at 443.6 keV in 182Ta was confirmed. Weisskopf hindrance factors have been deduced for the K- and Ω-forbidden transitions. The K-allowed transitions are considered in terms of the Nilsson model taking into account pairing correlations. The experimental results for the transitions de-exciting the 270.4 keV level in 182Ta agree with earlier model predictions including band mixing effects. The influence of the pairing effect on K-allowed E1 transitions in doubly odd nuclei is demonstrated. 相似文献
2.
In-beam measurements of nanosecond lifetimes applying the method of delayed γ-γ coincidences were performed in the (p, n) reaction. Analysing the time spectra with the centroid shift method, the following half-lives of excited nuclear states in the subnanosecond region could be found: , , , , , , , , , . Following half-lives in 173Lu have been remeasured: . Absolute γ-ray transition probabilities are deduced and compared with Nilsson model predictions including pairing correlations. Coriolis mixing calculations are performed for K-allowed as well as for K-forbidden transitions. 相似文献
3.
L.K. Kostov H. Rotter C. Heiser H. Prade F. Stary W. Andrejtscheff 《Nuclear Physics A》1982,376(3):451-462
Applying the generalized centroid shift method in (α, 2n) reactions, the half-lives of the 3080 keV 15+ state in 176Hf and of the 1637 keV 5? state in 178Hf have been measured as and , respectively. B(El) values of K-allowed E1 transitions are derived, and together with other data on similar transitions in odd-A nuclei, compared with predictions of the Nilsson plus pairing model. In 176Hf, the 15+ and 14? states at 3080 and 2866 keV, respectively, appear as quite pure deformed 4QP configurations. In the 2QP state at 1637 keV in 178Hf, possible strong mixing of vibrational components is discussed coupled via 2QP K-admixtures arising from the partial alignment of the neutron. 相似文献
4.
W. Andrejtscheff L.K. Kostov L.G. Kostova P. Petkov M. Senba N. Tsoupas Z.Z. Ding C. Tuniz 《Nuclear Physics A》1985,445(3):515-533
By the in-beam application of the generalized centroid shift method, nanosecond half-lives have been determined for the first time: in using the reaction , in using the reaction (16 O, αp), in using the reaction (16O,2np), in and in using the reaction P(α, xn). Some known nanosecond isomers in different nuclei produced as by-products have also been detected. In the nuclei investigated far away from closed shells with complex wave functions, M1 transitions are considered which would be l-forbidden in the pure shell model. A retarded transition in 91 Nb is considered as proceeding between possible multiparticle-hole configurations. 相似文献
5.
Using the reactions 155, 157Gd(α,2n), 178Hf(n,γ) and 177Hf(α, 2n, the following half-lives of excited nuclear states have been measured: , , , , , . A Ge(Li) timing system was employed. Electromagnetic transition probabilities are calculated in the Nilsson model including pairing and band mixing effects. Comparisons between theoretical and experimental results are performed. 相似文献
6.
W. Andrejtscheff L.K. Kostov H. Rotter H. Prade F. Stary M. Senba N. Tsoupas Z.Z. Ding P. Raghavan 《Nuclear Physics A》1985,437(1):167-188
Using the generalized centroid-shift method on the Rutgers tandem, the following half-lives of 106Cd excited states were measured in the reaction 93Nb(16O, p2n): . With the same method applied on the Rossendorf cyclotron, the following half-lives were measured in the reactions as well as , , , , , and . The results reveal the non-collective (two-quasiparticle) character of several states above 2.9 MeV in 104, 106, 108Cd, in qualitative accordance with predictions of the slightly-deformed-rotor model. They concern completely aligned [hg] (9??11?-13?, etc.) as well as semi-decoupled [hd] (6?-8?-10?, etc.) two-quasineutron band structures. Further, the possible character of 8+ (two-quasiproton) excitations, 5+ (two-quasineutron) states and of other intrinsic excitations is discussed. The experimental findings present a challenge to current theories of transitional nuclei for a quantitative treatment of absolute γ-ray transition strengths. 相似文献
7.
K.D. Schilling L. Käubler W. Andrejtscheff T.M. Muminov V.G. Kalinnikov N.Z. Marupov F.R. May W. Seidel 《Nuclear Physics A》1978,299(2):189-229
Nanosecond lifetimes of excited states in doubly odd deformed nuclei have been determined by in-beam measurements applying the method of delayed γ-γ coincidences as well as by experiments in the radioactive decay with the method of delayed γ-ce coincidences, respectively. Analysing the time distributions and delayed γ-ray spectra, the following half-lives of isomeric states could be obtained for the first time: . Furthermore, upper limits for the half-lives of fifteen excited states in 160Tb, 164, 166Ho and 186, 188Re have been estimated. For eight isomeric levels in 186, 188Re, the lifetimes earlier determined have been remeasured. Unlike previous studies, the existence of isomeric states at 87.2 keV in 156Ho and at 179.9 keV in 162Ho is suggested. Absolute γ-ray transition probabilities are deduced and compared with single-particle estimates according to Weisskopf and Nilsson, the latter also including pairing correlations. The K-, Ω- and f-forbidden transitions can qualitatively be explained in terms of configuration mixings. Experimental El, ΔK= 1 transition matrix elements in odd-odd deformed nuclei are supposed to be appreciably influenced by higher-order vibrational admixtures coupled via RPC and p-n interaction mixings. 相似文献
8.
In a study of the γ-radiation emitted in the reaction 176Yb(p, 2n) excited states of the nucleus 175Lu up to spin I = have been investigated. The main results concern the rotational bands + [411]and ? [541]with the corresponding band heads found at 626.60 and 370.88 keV, respectively. The half-life of the +[411] level has been determined to be . Furthermore, the band heads ?[532]and [411]are proposed at energies of 999.0 and 1150.8 keV, respectively. Experimental E1 transition probabilities between both bands are compared with calculations including the Coriolis and pairing effects, as well as theoretically deduced quadrupole deformation parameters. 相似文献
9.
O. Häusser T.K. Alexander T. Faestermann D. Horn D. Ward H.R. Andrews I.S. Towner 《Physics letters. [Part B]》1978,73(2):127-130
The time-differential perturbed angular distribution method was used to determine the g-factors of the states in 43Ti and 43Sc. The results for the mass 43 mirror pair are: , . Considering in addition the magnetic moments in A = 41 and 42, it is suggested that the deformed states considered by Johnstone and Castel and by Erikson are responsible for the observed large deviations from the Schmidt values. 相似文献
10.
The half-lives of the lowest + states in and were measured with the pulsed beam direct timing method. The results are and 1.61 ± 0.10 ns for and , respectively. The known experimental data on E2 transition rates in N = 50 nuclei are analysed in the light of a suggested seniority mixing in the proton . orbit. It is concluded that the E2 matrix elements cannot be explained satisfactorily in the proton model space, even if free seniority mixing is allowed. 相似文献
11.
C. Détraz D. Guillemaud G. Huber R. Klapisch M. Langevin F. Naulin C. Thibault L.C. Carraz F. Touchard 《Nuclear Physics A》1978,302(1):41-50
The 48K, 49K and 50K nuclides have been produced in high energy fragmentation and analyzed by mass spectroscopy techniques. Their half-lives have been measured as 6 ± 1 s, 1.1 ± 0.3 s and and 0.7 ± 0.3 s, respectively. The γ-rays from their radioactive decay have been observed and the corresponding γ-intensities measured. The nuclide 50K is shown to be a delayed neutron emitter. The antianalog states in the daughter Ca nuclei with a neutron configuration, preferentially populated in the β-decay, have been located. The corresponding neutron single-particle energy is found to remain approximately constant for these neutron-rich Ca isotopes. 相似文献
12.
Levels of 184W populated in the decay of 8.7 h 184Ta have been studied by a variety of experimental techniques. As a result of β and γ-ray energy and intensity determinations and extensive β-γ and γ-γ coincidence measurements, a detailed 184Ta decay scheme accommodating more than 99.5% of the decay intensity has been established. Intense β-ray groups of end-point energies 1165±26 and 1123±26 keV populate levels in 184W at 1699 and 1746 keV, which de-excite predominantly to the 8.3 μs isomeric level at 1285 keV, recently identified as the band origin. The 1699 keV level also de-excites to members of a band based at 1425 keV. New information about the properties of the γ-vibrational and K = 2 octupole bands in 184W is presented and the possible configurations of the levels directly populated in the β? decay are discussed. The configuration is indicated for the 184Ta ground state. 相似文献
13.
A. Filevich A. Ceballos M.A.J. Mariscotti P. Thieberger E. Der Mateosian 《Nuclear Physics A》1978,295(3):513-524
The 6? and 7? isomeric states in 66Ga and 68Ga at 1440.9 and 1229.6 keV, respectively, have been populated with the (13C, 2np) and (15N, n2p) reactions on natural Fe. The half-lives of these states have been measured to be and . Using previous data on the hyperfine field of Ga in Fe, the g-factors of these states have been determined by means of the TDPAD method. The results are and . These values are in very good agreement with the independent particle model if one assumes the and configurations and uses the empirical proton and neutron g-factors from odd-A neighboring nuclei instead of the Schmidt values. The large disagreements with experiment when Schmidt values are used show that core polarization effects are important in these nuclei. 相似文献
14.
U. Becker H. Kerkhoff M. Kwiatkowski M. Schmidt U. Teppner P. Zimmermann 《Physics letters. A》1980,76(2):125-127
A beam of metastable silicon atoms was produced by collisional dissociation of silicon molecules and selectively excited by a pulsed dye laser. The lifetimes of the excited Si I states were directly determined from the fluorescence decay curve: , , . 相似文献
15.
W.D. Fromm H.F. Brinckmann F. Dönau C. Heiser F.R. May V.V. Pashkevich H. Rotter 《Nuclear Physics A》1975,243(1):9-28
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 = 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 + of the isomeric state can be explained by the three-particle configuration [. 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 quasirotational band is experimentally proved and is supported by calculations of the equilibrium deformation. 相似文献
16.
17.
D.J. Decman H. Grawe H. Kluge K.H. Maier A. Maj N. Roy Y.K. Agarwal K.P. Blume M. Guttormsen H. Hübel J. Recht 《Nuclear Physics A》1985,436(2):311-337
The nucleus 217Ac was studied using the 205Tl(16O, 4n), 206Pb(15N, 4n) and 209Bi(12C, 4n) reactions. The mesurements included αγ, γγ, α-ce and ce-ce coincidence experiments as well as γ-ray and α-particle perturbed angular distribution studies. Results are and , the shortest known α-decay of a ground state. 217mAc decays mainly by a γ-cascade, but also by α-emission to the single-particle states of 213Fr. Spins and parities of levels to the + isomer at 2013 keV with and g = + 0.347(5) are determined. The level scheme of 217Ac and the α-decay of N = 128 isotones are discussed. 相似文献
18.
J. Rekstad M. Guttormsen T. Engeland G. Løvhøiden O. Straume J. Lien C.E. Ellegaard 《Nuclear Physics A》1979,320(2):239-259
The level structure of 153Sm has been studied by means of the 150Nd(α, n)153Sm reaction. The experiment included measurements of the γ-γ coincidences and γ-ray yield as a function of projectile energy. The rotational band built on the [505] Nilsson orbital was observed up to spin , and two ΔI = 2 bands of positive parity were identified with spins up to , respectively. These bands are associated with the single-particle structure.The data obtained in the present work together with data available in the literature are compared to the result of a particle-rotor coupling calculation. The 153Sm nucleus is found to be a wellbehaved rotor. An appropriate single-particle level scheme for 153Sm is established. 相似文献
19.
Nuclear g-factors of isomeric bandheads in the transition nuclei 119I and 192Tl have been measured to be and . These values are in agreement with a model of one or two quasiparticles coupled to a deformed core. This interpretation is also supported by a preliminary quadrupole moment determination of . The lifetimes were remeasured to be and for the 119I and the 192Tl isomers, respectively. 相似文献
20.
B. Fant T. Weckström T. Lönnroth C.J. Herrlander K. Honkanen A. Källberg 《Nuclear Physics A》1984,429(2):296-312
Levels in 208At were populated in the 209Bi(α, 5n) reaction, and the subsequent radiation was studied using γ-spectroscopic methods including γ-ray excitation function and angular distribution, γγ(t) coincidence and γt measurements, as well as measurements of conversion electrons. The excited spectrum of 208At is found to consist of two almost disconnected parts which are proposed to originate from seniority-three proton and neutron cascades. Two isometric states are observed. A state at 1090 keV is proposed to have the main configuration and Jπ = 10?. A high-spin isomer with is assigned to be the state. Shell-model arguments are used to assign configurations to most of the observed levels. Transition rates are discussed. 相似文献