Münster 2002 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 30: Nuclear Physics / Spectroscopy IV

HK 30.5: Vortrag

Mittwoch, 13. März 2002, 15:15–15:30, B

Mixed-symmetry excitations near the Z=38 sub-shell ^∗ — •V. Werner¹, D. Belic², P. von Brentano¹, C. Fransen¹, A. Gade¹, H. von Garrel², U. Kneissl², C. Kohstall², A. Linnemann¹, A. Lisetskiy¹, N. Pietralla¹, H.H. Pitz², M. Scheck², and F. Stedile² — ¹Institut für Kernphysik, Universität zu Köln — ²Institut für Strahlenphysik, Universität Stuttgart

Isovector excitations are particularly sensitive to the proton-neutron interaction, which plays a fundamental role in the nuclear many-body system, and which can well be studied, e.g., in light N=Z nuclei. The investigation of mixed-symmetry (MS) states as, e.g., described in the IBM-2 framework, gives a complementary approach to the study of the proton-neutron interaction in other, heavier open-shell even-even nuclei. The fundamental MS state, the low-lying one-phonon 2_ms⁺ state, has been identified in the N=52 nuclei ⁹⁴Mo [1] and ⁹⁶Ru [2]. We present new results of a photon scattering experiment on ⁹²Zr, performed at the Dynamitron accelerator of the Institut für Strahlenphysik in Stuttgart. Several J=1 and J=2 states of ⁹²Zr have been observed and the 2₂⁺ state has been identified as the one-phonon MS state based on its large M1-strength to the 2₁⁺ state. It is shown that the excitation energy of the 2_ms⁺ state is lowered systematically when approaching the Z=38 sub-shell closure. The discussed structures are also studied in the shell model, and the results support the MS character of the 2₂⁺ state of ⁹²Zr.

[1] N. Pietralla et al., Phys. Rev. Lett. 83, 1303 (1999).

[2] N. Pietralla et al., Phys. Rev. C 64, 031301(R) (2001). ^∗ gefördert durch die DFG, Sachbeihilfe Br799/9-3