Eur. Phys. J. A (2005) 24: 161-165
https://doi.org/10.1140/epja/i2004-10140-7

Original Article

First observation of excited states in the ¹¹¹Tc nucleus --A new region of deformation at 40 ⩽ Z ⩽ 46, N ≥ 68?

¹ Faculty of Physics, Warsaw University, ul. Hoża 69, 00-681, Warsaw, Poland
² Department of Physics and Astronomy, University of Manchester, M13 9PL, Manchester, UK
³ Argonne National Laboratory, 60439, Argonne, IL, USA

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

Received: 26 October 2004
Accepted: 2 March 2005
Published online: 17 March 2005

Abstract

The ¹¹¹Tc nucleus, populated in the spontaneous fission of ²⁴⁸Cm, was studied by means of prompt γ-ray spectroscopy using the EUROGAM2 array. Excited states in ¹¹¹Tc were observed for the first time. Systematics of energy levels in odd-A Tc isotopes, obtained in our study of ¹⁰⁷Tc and ¹⁰⁹Tc provide a reliable spin and parity assignment I = 5/2⁺ to the head of the new band in ¹¹¹Tc, interpreted as the π5/2⁺[422] orbital originating from the proton g _9/2 shell. This level is most likely the ground state. Therefore, the (9/2⁺,7/2⁺) spin-parity assignment to the ground state of ¹¹¹Tc, reported previously, is unlikely. Properties of the yrast band in ¹¹¹Tc suggest prolate deformation of this band. There are hints that the deformation of ¹¹¹Tc is larger than that of ¹⁰⁹Tc, possibly due to admixtures of oblate-deformed configurations, which lower their excitation energy with increasing neutron number.