共查询到20条相似文献,搜索用时 562 毫秒
1.
F. Glatz S. Norbert E. Bitterwolf A. Burkard F. Heidinger Th. Kern R. Lehmann H. Röpke J. Siefert C. Schneider B. H. Wildenthal 《Zeitschrift für Physik A Hadrons and Nuclei》1986,324(2):187-204
Theγ-decays of levels in26Mg have been investigated up to 12.5 MeV excitation energy by proton-γ-ray coincidence measurements in the23Na(α, pγ) reaction at 14.2 and 16 MeV bombarding energy. Lifetime-measurements, made with the Doppler-shift attenuation method, and proton-γ-ray angular-correlation measurements were performed at Eα=14.2 MeV. Many high-spin states were observed, among them levels at 6,978 (5+), 7,283(4?), 7,395(5+), 7,953(5?), 8,202(6+), 8,472(6+), 9,065(5), 9,112(6+), 9,169(6?), 9,383 (6+), 9,542(5), 9,829(7+), 9,989(6+) and 12,479(8+, 7?) keV excitation energy. The spectrum of positive-parity states and their electromagnetic properties are reproduced with good accuracy by shell-model calculations which employ a unifieds-d shell Hamiltonian and the unrestricted configuration space of the 0d 5/2 1s 1/2 0d 3/2 shell. Members of five inferred rotational bands, withK π=0+, 2+, 3+, 0+ and 3? have been observed up to at leastI=6. TheK π=2+ band shows strong anomalies of excitation energies andE2 transition rates near theI=6 state. The static intrinsic quadrupole moments calculated from the shell model wave functions indicate transitions from prolate to oblate deformation within theK π=2+ band and also the ground state band. The lowest lyingI π=4+ state appears to be “spherical” and cannot be associated with a rotational band. 相似文献
2.
N. L. Gjørup M. A. Bentley B. Fabricius A. Holm J. F. Sharpey-Schafer G. Sletten P. M. Walker 《Zeitschrift für Physik A Hadrons and Nuclei》1990,337(3):353-354
NewK-isomers with very high spin (up to 57/2) have been found in175Hf. This is the highest spin isomer seen in deformed nuclei and involves 9 quasi-particles. The predominant decay to the I=55/2 state in aK π=35/2?, 5 quasi-particle rotational band further demonstrates the surprising breakdown of theK-selection rules, reported previously in neighbouring nuclei. 相似文献
3.
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
4.
C. Fahlander G. de Angelis D. Bazzacco S. Beghini F. Brandolini D. Cline L. Corradi M. De Poli E. Farnea A. Gadea T. Härtlein S. Lunardi G. Montagnoli D. R. Napoli C. M. Petrache Z. Podolyák C. Rossi Alvarez F. Scarlassara A. M. Stefanini C. Y. Wu 《Acta Physica Hungarica A》1998,7(1):109-110
Two-phonon γ-vibrational states in166Er have been populated using Coulomb excitation. The Kπ=4+ component of the vibration appears to be fragmented over several states, whereas only one Kπ=0+ state is observed. 相似文献
5.
Investigation of vibrational levels in 226Ra by Coulomb excitation and by the 226Ra (d,pnγ) reaction
B. Ackermann Ch. Fleischmann H. Baltzer J. de Boer T. Czosnyka C. Günther U. Müller T. Weber 《Zeitschrift für Physik A Hadrons and Nuclei》1974,355(2):151-156
Vibrational bands in 226Ra were studied by Coulomb excitation and by the 226Ra(d,pnγ) reaction. The first-excited K π = 0+ and 1? bands with known band heads at 825 and 1049 keV, respectively, were extended up to the 8+ and 7? levels. A new 2+ level at 1110 keV and the known 2+ level at 1156 keV were observed following Coulomb excitation and interpreted as γ vibration and possible member of a second-exited K π = 0+ band, respectively. The E1 and E2 branching ratios from these vibrational bands to the ground and first-excited 0? band are explained within the rotational model including band mixings. No evidence was found for a 0+ level at 650 keV proposed earlier. 相似文献
6.
B. Ackermann Ch. Fleischmann H. Baltzer J. de Boer T. Czosnyka C. Günther U. Müller T. Weber 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):151-156
Vibrational bands in226Ra were studied by Coulomb excitation and by the226Ra(d,pnγ) reaction. The first-excitedK π = 0+ and 1? bands with known band heads at 825 and 1049 keV, respectively, were extended up to the 8+ and 7? levels. A new 2+ level at 1110 keV and the known 2+ level at 1156 keV were observed following Coulomb excitation and interpreted asγ vibration and possible member of a second-exitedK π = 0+ band, respectively. TheE1 andE2 branching ratios from these vibrational bands to the ground and first-excited 0? band are explained within the rotational model including band mixings. No evidence was found for a 0+ level at 650 keV proposed earlier. 相似文献
7.
The energy levels of 234U and 236U have been studied through the inelastic scattering of 16 MeV douterons. A magnetic spectrograph was used to momentum-analyse the scattered deuterons at θ = 90° and 125°. Excited in both 234U and 236U were the ground state bands up to and including the 8+ members, the Kπ = 0+β-vibrations, the Kπ = 2+γ-vibrations, and the Kπ = 0? octupole vibrational bands. In 234U, additional levels at 1023 and 1126 keV are ascribed to a Kπ = 2? band, levels at 1238, 1312, and 1446 keV are identified as members of either a Kπ = 0? or 1? configuration, and other tentative assignments are made for members of Kπ = 1? and 3? configurations. Relative reduced transition probabilities, B(E2), to the 2+ rotational and γ-vibrational states are generally found to be in good agreement with Coulomb excitation measurements. Relative B(E3) values for the 3? states excited are slightly higher than the predictions of a microscopic theory of octupole vibrations. 相似文献
8.
F. Glatz J. Siefert P. Betz E. Bitterwolf A. Burkard F. Heidinger Th. Kern R. Lehmann S. Norbert H. Röpke 《Zeitschrift für Physik A Hadrons and Nuclei》1981,303(3):239-251
A search for high-spin states in28Si has been performed byn?y coincidence measurements in the25Mg(α,nγy) reaction atE α=14 and 15.5 MeV. Spin-parity assignments of the observed levels were obtained fromn?γ angular correlation and lifetime measurements atE α=14.5 MeV. Theγ-decay of the 9,164 keV level was investigated separately with the27Al(p, γ) reaction at theE p=2,160 and 2,312 keV resonances. Rotational bands withK π=3? (comprising levels atE x=6,879, 8,413, 10,188 and 12,204 keV),K π =5? (comprising levels atE x=9,702, 11,577 and 13,741 keV) andK π=0+ (comprising levels atE x=6,691, 7,381, 9,164 and 11,509 keV) were observed. The finding of the latter band supports the idea of coexisting oblate and prolate shapes in28Si. A level at 14,643 keV excitation energy has the properties of theI π=8+ member of the ground state band. There are additional positive-parity high-spin states which do not fit into rotational bands. All types of positive-parity states are well accounted for by shell model calculations. 相似文献
9.
K. Hardt P. Schüler C. Günther J. Recht K. P. Blume 《Zeitschrift für Physik A Hadrons and Nuclei》1983,314(1):83-88
The ground state rotational bands in233U and239Pu were investigated in (α, 3n) reactions. Conversion electrons were measured with an iron free orange spectrometer in order to suppress the background from fission. Levels up toI π=33/2+ of theK=5/2 band in233U andI π=31/2+ of theK=1/2 band in239Pu were identified ine ?γ coincidence measurements. The level energies of both rotational bands can be well described up to the highest observed spins by a two-parameter angular velocity expansion. The electromagnetic properties of theK=1/2 band in239Pu are discussed. 相似文献
10.
A. Zilges P. von Brentano H. Friedrichs R. D. Heil U. Kneissl S. Lindenstruth H. H. Pitz C. Wesselborg 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(2):155-158
High resolution photon scattering experiments on various Nd-, Gd-, Dy-, Er- and Yb-isotopes yielded new information about the energy and absolute ΔK=0 groundstate transition strengths ofJ=1 levels with excitation energies between 1.5 and 4 MeV. The lowest of theseJ π=1? states are suggested to be the bandheads of aK π=0 ? octupole vibrational band, whereas the origin of the higher lying states is unknown. 相似文献
11.
《Nuclear Physics A》1999,660(2):121-170
The structure of the doubly-odd nucleus 180Ta has been studied by γ–γ coincidence measurements with a DC beam at 52 and 57 MeV and time-correlated γ–γ coincidence measurements with a pulsed beam at 55 MeV via the 176Yb(11B, α3n)180Ta reaction. In all measurements, γ-rays were detected in coincidence with charged particles. In the time-correlated γ–γ coincidence measurements with a pulsed 11B beam, three rotational bands and one octupole vibrational band have been identified above the Iπ=15− T1/2=30 μs isomer. The configuration of three bands built on 8+ states has been discussed by means of three-band mixing calculations. BCS calculations with blocking have been used in support of configuration assignment of four- and six-quasiparticle structures. Totally, 19 rotational bands, one β-, one γ- and two octupole-vibrational bands, plus one intrinsic state have been identified with two-, four- and six-quasiparticle configurations. The K values of these bands range from 0 to 19. The K-forbidden transition rates are discussed on the basis of mixing between states with widely different K-values. The BBCS calculations predict a Kπ=22− isomer not identified experimentally in this nor in previous works.A search for specific intermediate states which could explain the transformation from Kπ=9− to 1+ during the astrophysical s- and r- processes was negative. 相似文献
12.
The 230Th(α, α'2n)228Th reaction at Eα = 56 MeV was used to investigate states of moderately high spin in 228Th. Conversion electron and e?-γ coincidence measurements were carried out, where the electrons were detected with an iron-free orange spectrometer. The ground state and low-lying Kπ = 0? rotational bands were observed up to Iπ = 14+ and 13?, respectively. The data are interpreted in terms of an ω-expansion for the ground-state rotational band, and an octupole vibrational band distorted by the Coriolis coupling to the Kπ ? 1? excitations for the Kπ = 0? band. 相似文献
13.
F. Glatz M. Lickert A. Burkard Th. Kern R. Lehmann S. Norbert H. Röpke J. Siefert B. H. Wüdenthal 《Zeitschrift für Physik A Hadrons and Nuclei》1986,324(2):173-185
New shell model calculations have predicted several high-spin (I π=5+ and 6+) levels in28Si near 10 MeV excitation energy which are missing from or ambiguous in existing experimental studies. Angular distributions, linear polarizations and Doppler-shifts ofγ-rays have been measured for theγ-decay of theE p=1,911 and 2,073 KeV resonances of the27Al(p, γ) reaction in an attempt to discover these missing states or confirm the discrepancies between experiment and theory. The excitation energies and spin-parities of the resonances were determined as 13,424.4±0.2 keV,I π=5+ and 13,582.3±0.5 keV,I π=6+. States populated in theγ-decay of these resonances were assigned spins and parities as follows: 11,777 keV,I π=5+; 11,331 keV,I π=6+; 10,417 keV,I π=5+; 9,417 keV,I π=4+ and 8,945 keV,I π=5+. On the basis ofγ-ray transition rates T=1 is assigned to the 13,424 keV level and T=0 to the 10,417 and 11,777 keV levels. With the new data excellent agreement is achieved between the experimental spectrum of28Si and the new shell model predictions. These data provide evidence for aK π=3+ rotational band comprised by the 6,276, 6,889, 8,945 and 11,331 keV levels. This band emerges also from the shell model wave functions as do theK π=0+ bands based on the ground state and the 6,691 keV state. 相似文献
14.
J. Döring G. Winter L. Funke P. Kemnitz E. Will 《Zeitschrift für Physik A Hadrons and Nuclei》1982,305(4):365-366
Excited states of the doubly-odd nucleus V6Br have been studied with in-beam γ-ray spectroscopy techniques. In addition to the positive parity band that has been extended up to I=(13) a Iπ=4? isomer (T1/2=0.5±0.2 ns) and two bands of negative parity have been identified. The bands are discussed in terms of two-quasiparticle configurations. For the band built on the 4? isomer the configuration πg9/2?νf5/2 or p3/2 is proposed. 相似文献
15.
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
16.
Vibrational states built on the K π = 9? isomer and on the ground state (K π = 1+) in 180Ta are calculated within the quasiparticle-phonon nuclear model using the 178Hf nucleus as a core. A procedure for calculating the rates of K-allowed γ-ray transitions from vibrational states built on the isomer to those built on the ground state is presented. The probabilities of two-step processes consisting of a dipole excitation of the isomer and successive E1 and E2 transitions from them to vibrational states built on the ground state of the 180Ta nucleus are calculated. Two-step transitions from the isomer to vibrational states below 2.7 MeV and to the vibrational states built on the ground state appear to be very weak. There are many E1 transitions from the vibrational states built on the isomer to the vibrational states built on the ground state. They are weak and cannot be responsible for the strong deexcitation of 180m Ta in the relevant (γ, γ′) reaction. A decisive role is played by collective E2 transitions from dipole excitations in several excitation energy intervals ranging between 2.7 and 4.0 MeV. These highly intense K-allowed two-step γ-ray transitions can be responsible for the strong deexcitation of the 180m Ta state in the (γ, γ′) reactions. 相似文献
17.
P. Betz E. Bitterwolf B. Busshardt H. Röpke 《Zeitschrift für Physik A Hadrons and Nuclei》1976,276(3):295-302
The42Ca levels at 4,715 and 6,633 keV excitation energy have been investigated using the39 K(α,pγ reaction atE α=14 and 15 MeV. From particle-γ-ray angular correlations the spin assignmentsJ(4,715)=6, 4 andJ(6,633)=8, 6, 4 have been obtained. Lifetime measurements using the Doppler-shift attenuation method yieldedτ (4,715)=120±46 fs andτ(6,633)=52±21 fs. Both levels have positive parity and decay by enhancedE2 transitions. They are interpreted as theJ π=6+ and 8+ members, respectively, of theK π=0+ rotational band which has theE x =1,837, 2,423 and 3,250 keV states as further members. The enhancement of inbandE2 transitions is 50 ?16 +35 W.u. (6→4) and 63 W.u. (8→6) respectively. The intrinsic quadrupole moments which have been derived on the basis of the coexistence model, areQ 0=1.13?0.16/+0.37b(8→6) andQ 0=1.36±0.25b(6→4), respectively. TheJ π=10+ member of the rotational band has possibly been observed as a level at 8,856±5 keV excitation energy. 相似文献
18.
E. Bitterwolf A. Burkard P. Betz F. Glatz F. Heidinger Th. Kern R. Lehmann S. Norbert H. Röpke C. Schneider J. Siefert 《Zeitschrift für Physik A Hadrons and Nuclei》1983,313(1-2):123-132
Theγ-decay of40Ar has been studied by particle-γ-ray coincidence measurements in the37Cl(α, pγ) reaction at 12 and 13 MeV bombarding energy. Particle-γ-ray angular correlations and linear polarizations ofγ-rays were measured at 12 MeV. A lifetime measurement using the Doppler-shift attenuation method was performed at 11 MeV. The coexistence of spherical and deformed states in40Ar could be concluded from the observation of aK π=0+ rotational band which has itsI π=0+ through 6+ members at 2,121, 2,524, 3,515 and 4,959 KeV excitation energy. The intrinsic quadrupole moment derived fromB(E2) values is ∥Q 0∥=1,320 ?120 +60 mb. Negative-parity states with high spin were observed at 4,858(5?), 4,494(5?), 4,226(4?) and 4,991 KeV(4?) excitation energy. A complete account of all levels below 5 MeV excitation energy is obtained by a model in which twod 3/2 proton holes couple weakly to the42Ca levels below 4.75 MeV excitation energy. 相似文献
19.
M. S. Rouabah Th. Byrski F. A. Beck D. Curien B. Haas J. C. Merdinger J. P. Vivien J. Gizon B. Nyakó 《Zeitschrift für Physik A Hadrons and Nuclei》1987,328(4):493-494
High spin states in120Xe were populated in the reaction106Cd(18O, 4n) at a bombarding. energy of 90 MeV and the subsequent de- excitation was studied using γ- ray spectroscopic methods. New levels and several. spin and parity. assignments were established. The yrast band was observed up to theK π=22+state with two band crossins athw c=0.39MeV and 0.45Mev Negative parity levels and a new positive parity band were also identified. 相似文献
20.
From γ-ray linear polarization measurements, γ-ray angular distributions and γ?γ coincidences, the following levels were identified in 48V (EXin keV): 4? at 1099, (5?) at 1685, (6?) at 2397, (7?) at 3171 and (8?) at 3976. This sequence of states is interpreted as a Kπ = 4? rotational band. 相似文献