Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 10: Poster Session: Nuclear Structure/Spectroscopy

HK 10.25: Poster

Dienstag, 9. März 2004, 13:30–15:30, Foyer

Semiclassical Approach to describe the Competition between Magnetic and Collective Rotation in Transitional Nuclei — •A.A. Pasternak^1,2, R.M. Lieder¹, and E.O. Podsvirova^1,2 — ¹IKP, FZ Jülich, D-52425 Jülich — ²A.F. Ioffe PTI, RU-194021 St. Petersburg

The enhancement of M1 transitions can be explained semiclassically if high-j quasiparticles of angular momenta j₁ and j₂, respectively, are aligned along the principal axes x and z. The case, when collective rotation is absent, is referred to as magnetic rotation with shears effect. The collective rotation has been included into this model in the framework of a coupling scheme, when the angular momenta R and j₁ + j₂ are parallel to each other [1]. For transitional nuclei, where the deformation is not small, the shears mechanism can be combined with the PAC coupling scheme where the rotational angular momentum R is parallel to the symmetry axis (SPAC approach). The total energy contains collective and quasiparticle contributions: E(I,θ₁,θ₂) = 1/(2 J) R²(I,θ₁,θ₂) + V₂P₂(θ₁ − θ₂), where P₂ is a Legendre polynomial and R is determined geometrically. For each value of I the angles θ₁ and θ₂ can be found by the minimization of the total energy E. Subsequently, the transition probabilities B(M1) and B(E2) can be expressed as functions of I. The SPAC approach allows to describe the experimental data for dipole bands in ¹⁴²Gd and ¹⁴¹Eu including the bandcrossing.

[1] R.M. Clark et al., Ann. Rev. Nucl. Part. Sci. 50 (2000) 1

The work was partly supported by the German-Russian WTZ contract RUS 99/191.