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HK: Fachverband Hadronen und Kerne

HK 59: Nuclear Structure and Dynamics II

HK 59.6: Talk

Wednesday, March 18, 2009, 18:00–18:15, H-ZO 50

Shape coexistence in the neutron-rich isotope ¹³B with N = 8 studied by lifetime measurements of the excited states — •Hironori Iwasaki¹, Alfred Dewald¹, Christoph Fransen¹, Adrian Gelberg¹, Matthias Hackstein¹, Jan Jolie¹, Pavel Petkov^1,2, Thomas Pissulla¹, Wolfram Rother¹, and Karl-oskar Zell¹ — ¹IKP, Köln, Germany — ²INRNE, Sofia, Bulgaria

The lifetime measurement for the excited states in the neutron-rich nucleus ¹³B has been performed, at the FN tandem facility in the University of Cologne, by the Doppler-shift attenuation method with the ⁷Li(⁷Li,p)¹³B reaction. Anomalously hindered strength was found for the transition between the second excited states at 3.53 MeV and the ground state. A comparison with the modern shell model calculations suggests the spin and parity (J^π) of 3/2⁻ for the 3.53-MeV state with the hindered transition strengths to the ground state with J^π=3/2⁻, providing a consistent picture for the shape coexistence in the neutron-rich isotope ¹³B with N = 8. Experimental results will be presented and discussed in terms of the shell evolution in the light neutron-rich nuclei around N = 8.