Eur. Phys. J. A (2018) 54: 50
https://doi.org/10.1140/epja/i2018-12482-9

Regular Article - Experimental Physics

Lifetimes of excited states in triaxially deformed ¹⁰⁷Tc and ^109,111,113Rh

¹ Department of Physics, University of Oslo, Oslo, Norway
² Irfu, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
³ Grand Accélérateur National d’Ions Lourds (GANIL), CEA/DRF - CNRS/IN2P3, Bvd Henri Becquerel, 14076, Caen, France
⁴ Institut für Kernphysik, Universität zu Köln, Köln, Germany
⁵ Institute of Nuclear Sciences “Vinca”, University of Belgrade, Belgrade, Serbia
⁶ CSNSM, IN2P3, Orsay, France
⁷ Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy
⁸ Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Padova, Italy
⁹ INFN Sezione di Padova, Padova, Italy

^* e-mail: andreas.gorgen@fys.uio.no

Received: 23 December 2017
Accepted: 15 February 2018
Published online: 28 March 2018

Abstract

Lifetimes of excited states in ¹⁰⁷Tc, ¹⁰⁹Rh, ¹¹¹Rh, and ¹¹³Rh were measured at GANIL using the Recoil-Distance Doppler Shift method. The neutron-rich nuclei were produced in fission reactions in inverse kinematics with a ²³⁸U beam impinging on a ⁹Be target. Fission fragments were identified event-by-event in the ray-tracing spectrometer VAMOS++ and correlated with prompt rays observed around the target position with the EXOGAM Ge detector array. Several lifetimes were obtained for states in the positive-parity yrast bands in the four nuclei and compared to triaxial particle-rotor calculations. The results clarify the configuration for the strongest positive-parity band in ¹⁰⁷Tc and suggest a gradual increase of triaxial deformation with atomic number Z, reaching almost maximum triaxiality for the neutron-rich Rh nuclei.