Eur. Phys. J. A (2010) 44: 31-41
https://doi.org/10.1140/epja/i2010-10928-8

Regular Article - Experimental Physics

Isomerism of low-lying states in ⁸⁶Y

¹ Horia Hulubei National Institute of Physics and Nuclear Engineering, RO-077125, Bucharest, Romania
² School of Natural Sciences and Mathematics, University of Texas at Dallas, 75080, Richardson, TX, USA

^* e-mail: claudiu@utdallas.edu

Received: 26 October 2009
Revised: 11 January 2010
Accepted: 22 January 2010
Published online: 25 February 2010

Abstract

Low-energy isomeric states of ⁸⁶Y were populated in the reaction ⁷³Ge + ¹⁶O at 57MeV and were investigated by means of delayed n and coincidences. A half-life of 70(7)ns was measured for the 5^- state at 208keV, yielding an exceptionally small B(M1) value of 2.0(7)×10^-5 W.u. and a B(E2) value of 0.34(⁺²⁴ _-13) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5^- 208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6⁺, for this state. In addition, this re-evaluation provided two g -factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the f _5/2 , p _3/2 , p _1/2 , and g _9/2 valence orbitals. Effective spin, orbital, and “tensor” g -factors were determined empirically for protons and neutrons in the considered configuration space.