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1.
《Nuclear Physics A》1987,465(3):506-528
High-spin states in 154Dy have been studied using the TESSA2 γ-rays spectrometer following the 110Pd(48Ca,4n)154Dy reaction at a beam energy of 210 MeV. States up to 44+ and 37− have been observed. Below spin 30 the data display regular rotational behaviour which can be interpreted in terms of the cranked shell model. Above spin 30, sequences of levels connected by stretched E2 transitions, which show large gains in energy when compared to a rotating liquid drop reference, are lowest in energy for both parities. Particularly low energy levels are observed for spin Iπ = 36+ and 42+ and in addition dipole transitions are found connecting negative-parity states around spin I = 35. The experimental data for I ≳ 30 are compared with calculations, based on the Nilsson-Strutinsky cranking formalism, in which it is possible to trace fixed configurations through a sequence of spins. For the high-spin positive-parity sequence, the similarity with the 156Er spectrum is discussed. 相似文献
2.
A. Bäcklin G. Hedin B. Fogelberg M. Saraceno R.C. Greenwood C.W. Reich H.R. Koch H.A. Baader H.D. Breitig O.W.B. Schult K. Schreckenbach T. Von Egidy W. Mampe 《Nuclear Physics A》1982,380(2):189-260
Levels up to 2.3 MeV in 156Gd have been studied using the (n, γ) reaction. Energies and intensities of low-energy γ-rays and electrons emitted after thermal neutron capture have been measured with a curved-crystal spectrometer, Ge(Li) detectors and a magnetic electron spectrometer. High-energy (primary) γ-rays and electrons have been measured with Ge(Li) detectors and a magnetic spectrometer. The high-energy γ-ray spectrum has also been measured in thermal neutron capture in 2 keV resonance neutron capture. The neutron separation energy in 156Gd was measured as Sn = 8535.8 ± 0.5 keV.About 600 transitions were observed of which ~50% could be placed in a level scheme containing more than 50 levels up to 2.3 MeV excitation energy. 42 of these levels were grouped into 15 excited bands. In addition to the β-band at 1050 keV we observe 0+ bands at 1168, 1715 and 1851 keV. Other positive-parity bands are: 1+ bands at 1966, 2027 and 2187 keV; 2+ bands at 1154 (γ-band) and 1828 keV; and 4+ bands at 1511 and 1861 keV. Negative-parity bands are observed at 1243 keV (1?), 1366 keV (0?), 1780 keV (2?) and 2045 keV (4?). Reduced E2 and E0 transition probabilities have been derived for many transitions. The ground band, the β- and γ-bands and the 0+ band at 1168 keV have been included in a phenomenological four-band mixing calculation, which reproduces well the experimental energies and E2 transition probabilities.The lowest three negative-parity (octupole) bands of which the 0? and the 1? bands are very strongly mixed, were included in a Coriolis-coupling analysis, which reproduces well the observed energies. The E1 transition probabilities to the ground band are also well reproduced, while those from the higher-lying 0+ bands to the octupole bands are not reproduced. Absolute and relative transition probabilities have been compared with predictions of the IBA model and the pairingplus-quadrupole model. Both models reproduce well the E2 transitions from the γ-band, while strong disagreements are found for the E2 transitions from the β-band. The IBA model predicts part of the decay features of the higher lying 2+2, 4+1 and 2?1 bands. 相似文献
3.
Y. El Masri R. Janssens C. Michel P. Monseu J. Steyaert J. Vervier 《Zeitschrift für Physik A Hadrons and Nuclei》1975,274(2):113-119
Study of the energy levels of156Dy through the159Tb(p, 4n)156Dy reaction has revealed the existence of six states with excitation energies between 1.8 and 2.8 MeV and spins between 6 and 12. Some of them can tentatively be assigned as low-spin members of “upper” bands which are thought to be responsible for the backbending phenomenon experimentally observed in the ground-state andβ-vibrational bands of this nucleus. Others could be levels of a negative-parity octupole band. 相似文献
4.
P. Ekström B. Erlandsson A. Marcinkowski J. Tillman 《Zeitschrift für Physik A Hadrons and Nuclei》1972,252(3):189-205
The gamma-ray decay of the 1658 keV resonance, which is a member of the isobaric analogues of the 1904 keV 3/2? level in44Ca, has been studied with a Ge(Li) detector. A number of gamma-ray transitions are described and associated with the decay of 15 levels between 1.50 and 3.05 MeV. These observations have made it possible to deduce spin and parity assignments to some of the levels. By comparing excited levels of43Sc and45Sc it has been possible to assign certain levels as members of one negative-parity band and two positive-parity bands withK π=1/2+ and 3/2+. 相似文献
5.
《Nuclear Physics A》1987,465(1):1-24
The 158Gd(α, 2n)160Dy reaction has been used to study rotational side bands in 160Dy. Several negative-parity bands are observed, with several members of Kπ = 1−, 2− and 4− bands and of a Kπ = 8− band only the bandhead. A pronounced odd-even staggering of moments of inertia is found for members of the Kπ = 2− band. Of the positive-parity bands the Kπ = 2+ (γ) band, which is seen up to a possible spin of 12 and low-spin members of Kπ = (0+), (S), and 4+ bands are observed. The mixing between most of the γ-band and S-band members is observed to be smaller than 2% and no evidence for possible anti-alignment of low-spin S-band members with rotation is found. 相似文献
6.
Y. El Masri J.M. Ferté R. Janssens C. Michel P. Monseu J. Steyaert J. Vervier 《Nuclear Physics A》1976,271(1):133-161
Using the 159Tb(p, 4nγ)156Dy reaction at Ep = 27 to 51 MeV and standard on-line γ-ray spectroscopy methods, the energies and decay properties of members of various rotational bands in the nucleus 156Dy have been investigated, i.e. the ground-state band up to 14g+, the β-vibrational band up to 14β+,the γ-vibrational band up to 11γ+,and two other bands, one with odd-spin levels up to 11, the other with even-spin levels up to 10. The results are compared with various calculations in the framework of the collective model, and no satisfactory fit is obtained; possible improvements of the model to remove these discrepancies are suggested. 相似文献
7.
Jan Konijn F.W.N. De Boer A. Van Poelgeest W.H.A. Hesselink M.J.A. De Voigt H. Verheul O. Schölten 《Nuclear Physics A》1981,352(2):191-220
A complete set of conventional γ-ray spectroscopic techniques has been applied to investigate the level structure of 156Gd. A total of twenty-five new levels has been established; unambiguous spin assignments could be given for twelve of them on the basis of angular distributions and conversion electron measurements. The proposed level scheme contains 49 levels, which can be ordered in seven rotational bands. The ground-state band was excited up to Jπ = 14+, the β-band up to 10+, the γ-band up to (11+), the second Kπ = 0+ band tentatively up to (10+), the Kπ = 4+ band up to (8+). Two negative-parity bands, one with even spins and one with odd spins, were excited to Jπ = (12?) and (13?). An isomeric state was established with . The properties of the Kπ = 4+ band and the isomeric state can be well explained by two-quasiparticle configurations. The negative-parity bands are interpreted as aligned octupole bands. Positive and negative-parity bands have been calculated in terms of the IBA model. Good agreement with the experimental results is obtained. 相似文献
8.
HUA Hui LI Zhong-Yu WANG Shou-Yu MENG Jie LI Zhi-Huan LI Xiang-Qing XU Fu-Rong LIU Hong-Liang ZHANG Shuang-Quan ZHOU Shan-Gui YE Yan-Lin JIANG Dong-Xing ZHENG Tao ZHU Li-Hua WU Xiao-Guang LI Guang-Sheng HE Chuang-Ye MA Li-Ying LU Fei FAN Feng-Ying HAN Li-Ying WANG He XIAO Jun LI Xue-Qin CHEN Dong FANG Xiao LOU Jian-Lin LIU Ying HAO Xin PAN Bo LI Li-Hua 《中国物理C(英文版)》2009,33(Z1)
High-spin states of 156Yb have been studied via the 144Sm(16O,4n)156Yb fusion-evaporation reaction at beam energy 102 MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25- state may related to the excitation from the nucleon in the Z = 64, N = 82 core. The E-GOS curve for the positive-parity yrast sequence in 156Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change. 相似文献
9.
K. Amos W. Bauhoff I. Morrison S.F. Collins R.S. Henderson B.M. Spicer G.G. Shute V.C. Officer D.W. Devins D.L. Friesel W.P. Jones 《Nuclear Physics A》1984,413(2):255-289
Differential cross sections have been measured for the scattering of 135 MeV protons from 16O and data from the transitions to 13 states (up to 19.5 MeV excitation) have been analysed using microscopic and macroscopic nuclear reaction models. Extensive collective model calculations have been made of the transitions to all natural-parity states. The deformation parameters for the 4p4h rotational band are in good agreement with theoretical models. The inelastic scattering data from the excitation of the negative-parity states have also been analysed in the distorted-wave approximation using microscopic (shell and RPA) models of nuclear structure and with density-dependent two-nucleon t-matrices. For positive-parity states, we report the first shell-model calculation using the complete 2?ω basis space and find that the triplet of 2p2h states (4+, 2+, 0+) around 11 MeV excitation is quite well described by this model, as may be a 1+ state which is observed for the first time by proton scattering from 16O. 相似文献
10.
R. Geiger P. von Brentano H. G. Friederichs B. Heits W. Schuh K. O. Zell H. Weigmann A. Berinde 《Zeitschrift für Physik A Hadrons and Nuclei》1974,271(2):129-137
The decay scheme of112Cd has been studied by γ-ray spectroscopy with the110Pd(α, 2nγ) reaction. Spin and parity assignments were made on the basis of coincidence measurements, angular distributions and excitation functions. Twelve new energy levels were established. A vibrational-like positive-parity band up to spin 8+ and a negativeparity side band 5?, (7?), (9?) were found. For the negative-parity states a (vj, vh11/2) configuration is suggested. Nuclear Reactions:110Pd(α,2nγ),E α =15–22.5 MeV; measuredE γ ,E γ , (E,E γ ),E γ (θ),γ-γ- coincidence;112Cd deduced levels,J; enriched target. 相似文献
11.
High spin states have been identified in 156Dy using (HI, xn) reactions and γ-γ coincidence techniques. The ground state band does not show any “phase change” or “back bending” behaviour up to spin 18+. However a second sequence, based on the β-vibrational band, does show back bending at spin 12+. The two sequences intersect just below spin 16+ with the 16+, 18+ and 20+ members of the β-band sequence becoming yrast levels. Branching ratios have been obtained for transitions above and below the bend at spin 12+. The data are discussed in terms of a simple band-crossing model of back bending. 相似文献
12.
The data on high-spin rotational states in155Dy,157Dy,159Dy and161Dy are discussed within a model where a particle is coupled to a rotor with a variable moment of inertia. In this model there is often a definite improvement in the quality and stability of the fits to levels in the positive-parity band below spin 25/2 when the moment of inertia of the core exhibits a linear dependence on the square of the rotational angular velocity as compared to the situation where a linear dependence onI(I+1) is assumed. In the improved fits the empirical matrix elements of the Coriolis force exhibit a smooth and significant increase with decreasing moment of inertia. The rotational energies above spin 25/2 in the positive-parity band and above 19/2 in the 11/2? [505] band are understood within the present theoretical model if the moment of inertia increases more rapidly than the linear trend established at lower spin. In the 11/2? [505] band this increase follows rather closely the behaviour in the even nuclei whereas in the positive-parity band the curves are quite flat even beyond the point where the moment of inertia in the even nuclei exhibits a discontinuous or back-bending behaviour. The significance of this observation is discussed in the light of existing theories on nuclear moments of inertia. 相似文献
13.
Quasi-band structures in 74Se, 78, 80Kr and 84Sr have been investigated using (p, 2nγ) reactions. The members of the quasi-γ band have been observed up to 5+ in 74Se, 78, 80Kr and up to 3+ in84Sr. The analyses of the energy systematics of the quasi-γ bands studied in this mass region as well as in other regions make clear the evolution of the quasi-γ band to the γ-band in well-deformed nuclei. In addition to these positive-parity bands, negative-parity levels were observed in 74Se, 80Kr and 84Sr. 相似文献
14.
R.N. Oehlberg L.L. Riedinger A.E. Rainis A.G. Schmidt E.G. Funk J.W. Mihelich 《Nuclear Physics A》1974,219(3):543-562
Coulomb excitation measurements with 16O and 4He projectiles have been performed on 160Dy, 162Dy, and 164Dy. The ground-state rotational bands up through the 8+ member were observed in the 16O experiments. The measured excitation probabilities yield B(E2; I → I ?2) values which are generally in agreement with the rotational predictions except for the 6+ → 4+ values. In each nucleus, probabilities for exciting the 2+, 4+, and 6+ members of the γ-vibrational band were measured and compared with calculated results. The B (E2; 0+ → 2+γ) values were measured in experiments involving 4He ions. The Kπ = 2? octupole band was observed in each nucleus in addition to 1? bands in 160Dy and 162Dy. Excitation probabilities were analyzed in an attempt to extract B(E3) values. 相似文献
15.
A. Celler Ch. Briançon J.S. Dionisio A. Lefebvre Ch. Vieu J. Żylicz R. Kulessa C. Mittag J. Fernandez-Niello Ch. Lauterbach H. Puchta F. Riess 《Nuclear Physics A》1985,432(2):421-435
Yrast states in the nucleus 220Ra were studied by means of the 208Pb(14C, 2n) reaction at 61 and 64 MeV. A staggering sequence of levels of positive and negative parity has been observed up to spin and parity Iπ = 16+ (18 +) and from Iπ = 5? to Iπ = 17?, respectively. These states are connected by strong E1 transitions competing with the stretched E2 transitions, the ratio being ~ 10 ?6 fm?2. The ratio of the excitation energy of the 4+ state to that of the 2+ state is close to the vibrational limit. The moment of inertia associated with the negative-parity yrast states is slightly increasing with the rotational frequency ω. It is considerably higher than that of the positive-parity states at lower spins, the difference decreasing monotonically with increasing ω. The data are discussed with reference to the octupole vibrational picture as well as to the results of recent models predicting reflection-asymmetric shapes in the Ra-Th region. 相似文献
16.
D. Proetel D. Benson A. Gizon J. Gizon M.R. Maier R.M. Diamond F.S. Stephens 《Nuclear Physics A》1974,226(2):237-252
The schemes of the low-lying high-spin states in mercury isotopes with A = 195, 197, and 199 have been studied by γ-ray spectroscopy following (α, xn) reactions on separated platinum targets. Two bands have been excited in each Hg nucleus, one with positive parity based on the isomeric i. state and one, probably with negative parity, starting at spin . The positive-parity states are interpreted with the rotation-aligned coupling scheme as decoupled bands; this implies oblate deformation in these three Hg isotopes. The negative-parity states are discussed as a decoupled i neutron state coupled to the 5?, 7?, 9?,…states, recently discovered in doubly even mercury isotopes. 相似文献
17.
M. Kortelahti R. Julin J. Hattula A. Pakkanen M. Piiparinen 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(3):417-424
Levels of135Pr populated in the (p,2n) reaction were studied using methods of in-beamγ-ray and conversion electron spectroscopy. Many low-lying positive-parity states give evidence of a deformation ofβ=0.15–0.20. The same conclusion is evident from band structures built on these positive-parity states and on theh 11/2 negative-parity state. The triaxial rotor-plus-particle model reproduces quite well band structures withβ=0.20 andγ= 21°. 相似文献
18.
High-spin yrast and non-yrast states have been identified in 176Os, 178Os and 180Os using (16O, xn) reactions, and γ-ray techniques. Band crossing anomalies are observed in each of the positive-parity yrast bands. The magnitude of these anomalies decreases with decreasing neutron number, an effect attributed to the change in the moment of inertia of the ground state rotational bands. A 23 ns isomer, predominantly Kπ = 7?, is identified at 1930 keV in 180Os. The configuration of this isomer is discussed on the basis of the properties of its rotational band. Negative parity, odd and even spin, sideband sequences are observed in each isotope. Their relationship to rotation-aligned octupole and 2-quasiparticle bands is discussed from their excitation energies, band spacings, and decay properties. Detailed calculations for Coriolis mixed bands are carried out for the likely 2-quasiproton and 2-quasineutron configurations. An anomaly observed at spin 17 in the odd-spin negative-parity sequence in 180Os is attributed to a band crossing with a fourquasiparticle configuration. 相似文献
19.
E. P. Grigoriev 《Physics of Atomic Nuclei》2008,71(8):1319-1324
Available experimental data on excited levels of the 148Ce nucleus are analyzed. With the aid of model concepts and systematics that cover neighboring nuclei, the spectrum of 148Ce is supplemented with a K π = 2? rotational band that has a bandhead at 1368.98 keV, which extends up to the 16? state at 3897.9 keV, and which is new. Three states at E = 1422.85, 1786.57, and 2198.6 keV of spin-parity 5+, 7+, and 9+, respectively, are included in the gamma-vibrational band featuring the known 2+ and 3+ levels at 989.90 and 1116.63 keV, respectively. A significant difference in the behavior of the moments of inertia in positive-and negative-parity bands is highlighted. 相似文献
20.
R. Kulessa Ch. Briançon A. Lefebvre C. F. Liang J. P. Thibaud R. J. Walen A. Celler Ch. Lauterbach J. De Boer Ch. Mittag F. Riess Ch. Schandera H. Emling S. Hlavač R. S. Simon I. N. Mikhailov Ph. N. Usmanov 《Zeitschrift für Physik A Hadrons and Nuclei》1989,334(3):299-314
The Coulomb excitation measurements for the230Th nucleus with32S,84Kr and142Nd projectiles are presented. The use of different projectiles allowed us to get information in the ground-state band and side bands. The energy spectrum of the ground-state band and of the lowest negative-parity band have been investigated up to the spin valueI=24+ andI=19?(21), respectively. Five side bands (K π=0+, 2 1 + , 2 2 + , 1?, 2?) were observed also. The branching ratios for a large number of transitions in the spin regionI≦10 for π=+1 andI≦9 for π=? 1 are analysed. The full set of experimental data contains information on the mixing of the adiabatic states and on the nuclear response to the electromagnetic field ofγ-radiation. It is shown that the experimental data may be explained taking into account the coupling of the ground-β- and twoγ-bands and also of theK π=0?, 1? and 2? negative-parity bands. An enhancement of the transitions from theγ-to theβ-band in respect to the transitions from theγ to the ground band and from theβ- to the ground band is reported. The mixing of the negative-parity bands is found to be typical for the alignment of the octupole-vibrational angular momentum. The strong spin dependence of the intrinsic matrix elements of the electric-dipole operator follows from the branching ratios of inter- and intra-band transitions from theK π=0? states. 相似文献