Nuclear data sheets for A = 156

Burrows, T.W.

doi:10.1016/s0090-3752(76)80012-9

Cited by 19 publications

(1 citation statement)

References 114 publications

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“…Since the 1--state in question was discovered in the inelastic electron scattering on nuclei it is useful to give the expression for the magnetic orbital form factor [131 T~ g (q) = i/(]/2Mp c) 9 ~d 3 r pp(r)(r x v,(r))V (Ja (qr) gl,(& (P)) (14) within the present model. Assuming the proton mass density of the form (15) and the irrotational velocity field vv(r ) we finally obtain…”

Section: The Angular Momentum Magnetic Form Factor and Magnetic Tranmentioning

confidence: 99%

Magnetic dipole excitation mode according to the collective model with separate neutron and proton deformations

Rohoziński

Greiner

1985

Z Physik A

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The collective model with separate neutron and proton deformations is developed. The collective motion of individual neutron and proton surfaces is reduced to the motion of the mass surface and the neutron skin. The strong coupling scheme of the neutron skin vibrations to the mass-surface motion is applied for well-deformed nuclei. The magnetic dipole excitation mode, which was discovered experimentally, is explained as the K--1 one-phonon neutron skin vibration in a deformed nucleus. Some estimates of parameters of the model are performed. Finally, the model is confronted with the two-rotor model and the interacting boson model (IBM-2). PACS: 21.60 EvRecently, a new collective, relatively low lying, l + state in deformed nuclei (156'15SGd) was discovered [1,2]. The existence of such a state has been predicted within two models of the collective excitations, namely the two-rotor model (TRM) [3,4] and the interacting boson model (IBM-2) [5,6], both treating the collective motion of neutrons and protons separately. The aim of the present paper is to show how such a magnetic 1 + state is described in the frame of the collective model dealing with separate neutron and proton deformations. The model was proposed for an explanation just magnetic properties of nuclei [7][8][9] and next also used for an analysis of electric transitions [10]. We shall hereafter refer to this model as the neutron-proton deformation (NPD) model. We start with a discussion of the general structure of NPD in Sect. 1. An approximate solution, good for well-deformed nuclei, of the model is presented in Sect. 2. Some estimates of parameters for 156Gd are performed in Sect. 3. Finally, in Sect. 4 NPD is compared with both TRM and IBM-2.

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Section: The Angular Momentum Magnetic Form Factor and Magnetic Tranmentioning

confidence: 99%

Magnetic dipole excitation mode according to the collective model with separate neutron and proton deformations

Rohoziński

Greiner

1985

Z Physik A

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Proton-neutron vibrations in the collective model

El-Din

Rohoziński

Maruhn

et al. 1987

Symmetries and Semiclassical Features of Nuclear Dynamics

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An anomalous behaviour of the gamma band in156Dy

Peker

Boer²,

Konijn³

1977

Z Physik A

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Analysis of the anomalous behaviour of the gamma band in 156Dy demonstrates the interference of the effect of 'internal' Coriolis coupling and quadrupole (AK = 2) coupling.The level energies of the rotational band built on a gamma-vibrational K=2 + state of an even-even deformed nucleus can be described by the formula: Ex=E o + A I(I + I)+ B I(I + I)The coefficient D is a measure of the odd-even shift. A measure of the strength of the non-adiabaticity (third and fourth term above) is AS = Sox p-S,d~ab where E~(4 + ~2 +) S~xp=E~(3+~2+ ) and Saa~,b=2.33.Quadrupole coupling (AK=2) between the gamma band (K~=2 +) and the nearest K~=0 + band (often the beta-vibrational band) causes non-adiabaticity, with the even spins from both bands pushed away in opposite directions. If only quadrupole coupling were responsible for the odd-even staggering the signs of AS and D are expected to depend upon the relative position of the beta band with respect to the gamma band. If the beta band is located at lower excitation energy (type A) the signs will be positive, and reverse (type B). Nuclei of the type A mostly occur at the beginning of the deformed rare-earth region (A= 150-156), most other nuclei belong to type B. Peker and Hamilton tlJ now show that the gamma bands of nuclei of both types have a negative AS, implying that the 2 + and 4 + members are always pushed down with respect to the odd spin member. This evidently disagrees with the above explanation. Non-adiabatic effects in the gamma bands have also been explained m by 'internal' Coriolis coupling. The * Present Address: Nattmrkundig Lab~176 der Vrije Universiteit de Boelelaan 1081 Amsterdam-Buitenveldert The Netherlands microscopic wave functions of the gamma-vibrational level can be considered as a combination of twoquasiparticle configurations with K~=2 +. Among these configurations, some contain particles (or holes) with large j and small f2 responsible for a strong Coriolis coupling -e.g. neutron/13/2 or proton h9/2 configurations. In odd A nuclei it is well established that such nucleons cause strong non-adiabatic effects. These coupling effects must yield the same sign for AS and D in all even nuclei for A< 180. Data on i.e. 176Hfshow [,1] that this sign is negative. There is a tendency that [AS[, the strength of the non-adiabaticity increases with the i13/2 admixture [-11. For nuclei of type A the non-adiabatic effect from internal Coriolis coupling has a sign opposite to that arising from quadrupole mixing and a competition between these effects can be expected, reflected in the odd-even shift. The observed AS and D values indicate that in general the internal Coriolis n (/13/2) effect is stronger than the quadrupole coupling effect (AK = 2), at least for the lower spin part of the gamma band. In those nuclei of type A where beta-and gamma bands are very close, the quadrupole coupling effect must yield strong (destructive) interference. A good canditate for the observation of such a competition is 156Dy, where the 2 + members are only 62 keV apart. Members of t...

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Nuclear data sheets for A = 156

Cited by 19 publications

References 114 publications

Magnetic dipole excitation mode according to the collective model with separate neutron and proton deformations

Magnetic dipole excitation mode according to the collective model with separate neutron and proton deformations

Proton-neutron vibrations in the collective model

An anomalous behaviour of the gamma band in156Dy

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