Shape coexistence in the neutron-deficient mercury isotopes studied through Coulomb excitation

This thesis describes the analysis and results of a series of Coulomb-excitation experiments on even-even neutron-deficient mercury isotopes aimed at obtaining a more detailed description of shape coexistence. Two experimental campaigns have been undertaken in the Summer of 2007 and 2008. Pure beams of 182,184,186,188Hg were produced and accelerated at the REX-ISOLDE radioactive-beam facility, located at CERN (Geneva, Switzerland). The beams were guided to collide with a stable target to induce Coulomb excitation. The scattered particles were registered by a double-sided silicon strip detector, and the emitted gamma rays by the MINIBALL gamma-ray spectrometer. The motivation to study these mercury isotopes, focused around shape coexistence in atomic nuclei, is addressed in chapter 1, as well as an overview of the knowledge in this region of the nuclear chart. A theoretical description of Coulomb excitation is presented in the second chapter, while the third chapter describes the setup employed for the experiments. The fourth chapter focusses on how the raw data have been analyzed. A study of observed, characteristic mercury K X-rays is described in chapter 5. The further analysis per investigated isotope and the resulting matrix elements are presented in chapter 6. Chapter 7 gives a possible interpretation of the results, and a comparison with theoretical work. The results of this work have been published in:N. Bree, K. Wrzosek-Lipska, A. Petts, A. Andreyev, B. Bastin, M. Bender, A. Blazhev, B. Bruyneel, P. A. Butler, J. Butterworth, M. P. Carpenter, J. Cederkäll, E. Clément, T. E. Cocolios, A. Deacon, J. Diriken, A. Ekström, C. Fitzpatrick, L. M. Fraile, Ch. Fransen, S. J. Freeman, L. P. Gaffney, J. E. Garcia-Ramos, K. Geibel, R. Gernhäuser, T. Grahn, M. Guttormsen, B. Hadinia, K. Hadynska-Klek, M. Hass, P.-H. Heenen, R.-D. Herzberg, H. Hess, K. Heyde, M. Huyse, O. Ivanov, D. G. Jenkins, R. Julin, N. Kesteloot, Th. Kröll, R. Krücken, A. C. Larsen, R. Lutter, P. Marley, P. J. Napiorkowski, R. Orlandi, R. D. Page, J. Pakarinen, N. Patronis, P. J. Peura, E. Piselli, P. Rahkila, E. Rapisarda, P. Reiter, A. P. Robinson, M. Scheck, S. Siem, K. Singh Chakkal, J. F. Smith, J. Srebrny, I. Stefanescu, G. M. Tveten, P. Van Duppen, J. Van de Walle, D. Voulot, N. Warr, F. Wenander, A. Wiens, J. L. Wood, and M. Zielinska.Shape Coexistence in the Neutron-Deficient Even-Even 182-188Hg Isotopes Studied via Coulomb Excitation, Physical Review Letters 112, 162701 (2014)