Eur. Phys. J. A (2005) 25: 123-124
https://doi.org/10.1140/epjad/i2005-06-040-2

ENAM 2004

On the structure of the anomalously low-lying 5/2⁺ state of ¹³⁵Sb

¹ Institute of Experimental Physics, Warsaw University, Warsaw, Poland
² Department of Radiation Sciences, Uppsala University, Uppsala, Sweden
³ Department of Physics and Astronomy and NSCL, Michigan State University, East Lansing, MI, USA
⁴ Dipartimento di Scienze Fisiche, Università di Napoli Federico II and Istituto Nazionale di Fisica Nucleare, Napoli, Italy
⁵ Department of Physics, University of Konstanz, Konstanz, Germany
⁶ Institut Lave-Langevin, Grenoble, France
⁷ Schulster Laboratory, University of Manchester, Manchester, UK

^* e-mail: korgul@fuw.edu.pl

Received: 20 December 2004
Accepted: 18 February 2005
Published online: 3 May 2005

Abstract

Recently the first-excited state in ¹³⁵Sb has been observed at the excitation energy of only 282keV and, due to its properties, interpreted as representing mainly a configuration of a d _5/2 proton coupled to the ¹³⁴Sn core. It was suggested that its low-excitation is due to a relative shift of the proton d _5/2 and g _7/2 orbits due to the neutron excess. With the aim to provide more spectroscopic information on this anomalously low-lying 5/2⁺ state, we have measured its lifetime by the Advanced Time-Delayed βγγ(t) method at the OSIRIS fission product mass separator at Studsvik. The preliminarily measured half-life, T _1/2 = 6.0(7)ns, yields an exceptionally low B(M1;5/2₁ ⁺ → 7/2₁ ⁺) value of ≤2.9×10^-4μ² _N. The result is discussed in the framework of shell model calculations.