Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 10: Poster Session: Nuclear Structure/Spectroscopy

HK 10.13: Poster

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

Direct proof of the |2⁺⊗ 3⁻⟩-two phonon character of the 1₁⁻-state in ¹⁴⁰Ce^* — •T. Hartmann¹, M. Babilon^1,2, R.F. Casten², J. Hasper¹, A. Hecht², M. Caprio², and A. Zilges¹ — ¹Institut für Kernphysik, TU Darmstadt, Germany — ²Physics Department - Wright Nuclear Structure Laboratory, Yale University, New Haven, CT, USA

A (p,p’γ)-experiment has been performed at the ESTU tandem accelerator at Yale University using 9 high resolution Ge(HP) Clover-detectors and 4 proton detectors to investigate the decay pattern of the first excited J^π=1⁻-state in ¹⁴⁰Ce. As in its N=82-isotones ¹⁴²Nd and ¹⁴⁴Sm this level is expected to be the member of a quintuplett of negative parity states arising from the coupling of two phonons (2₁⁺⊗ 3₁⁻) representing surface oscillations. The two phonon character of this collective isoscalar mode had been confirmed for ¹⁴²Nd and ¹⁴⁴Sm, by measuring the branching ratio of its decay to the 3₁⁻-state, where the branching ratio is 0.8% and 1.1%, respecitvely [1]. To proof the two-phonon character of this state in ¹⁴⁰Ce, a branching ratio of only 0.4% had to measured.
^* supported by the DFG (SFB 634 and Zi510/2-2) and by the US DOE (DE-FG02-91ER-40609)

[1] M. Wilhelm et al., Phys. Rev. C54 (1996) 449R.