Collectivity in the light radon nuclei measured directly via Coulomb excitation

Gaffney, L.P.; Orlandi, R.; Deacon, A.N.; Smith, J.F.; Bender, M.; Fransen, Ch.; Heenen, P. -H.; Konki, J.; Ekström, A.; Ivanov, O.; Davinson, T.; Wimmer, K.; Wrzosek-Lipska, K.; Hass, M.; Freeman, S.J.; Diriken, J.; Kröll, Th.; Jakobsson, U.; Pakarinen, J.; Bruyneel, B.; Van Duppen, P.; Scheck, M.; Wadsworth, R.; Hess, H.; Voulot, D.; Zielińska, M.; DiJulio, D.; Blazhev, A.; De Witte, H.; Martin-Haugh, S.; Mücher, D.; Kesteloot, N.; Warr, N.; Andreyev, A.N.; Seidlitz, M.; Hadinia, B.; Petts, A.; Jenkins, D.G.; Kumar, V.; Peura, P.; Huyse, M.; Singh, K.; Butler, P.A.; Bree, N.; Van de Walle, J.; Rahkila, P.; Cocolios, T.E.; Wenander, F.; Robinson, A.P.; Reiter, P.; Geibel, K.; Grahn, T.

doi:10.1103/PhysRevC.91.064313

Article
Report number	arXiv:1503.03245
Title	Collectivity in the light radon nuclei measured directly via Coulomb excitation
Author(s)	Gaffney, L.P. (Leuven U. ; Liverpool U.) ; Robinson, A.P. (York U., England ; Manchester U.) ; Jenkins, D.G. (York U., England) ; Andreyev, A.N. (Leuven U. ; York U., England ; JAEA, Ibaraki) ; Bender, M. (CENBG, Gradignan) ; Blazhev, A. (Cologne U.) ; Bree, N. (Leuven U.) ; Bruyneel, B. (Cologne U.) ; Butler, P.A. (Liverpool U.) ; Cocolios, T.E. (CERN ; Manchester U.) ; Davinson, T. (Edinburgh U.) ; Deacon, A.N. (Manchester U.) ; De Witte, H. (Leuven U.) ; DiJulio, D. (Lund U.) ; Diriken, J. (Leuven U.) ; Ekström, A. (Lund U.) ; Fransen, Ch. (Cologne U.) ; Freeman, S.J. (Manchester U.) ; Geibel, K. (Cologne U.) ; Grahn, T. (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Hadinia, B. (Paisley U.) ; Hass, M. (Weizmann Inst.) ; Heenen, P. -H. (Brussels U.) ; Hess, H. (Cologne U.) ; Huyse, M. (Leuven U.) ; Jakobsson, U. (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Kesteloot, N. (Leuven U. ; SCK-CEN, Mol) ; Konki, J. (CERN ; Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Kröll, Th. (Darmstadt, Tech. Hochsch.) ; Kumar, V. (Weizmann Inst.) ; Ivanov, O. (Leuven U.) ; Martin-Haugh, S. (York U., England) ; Mücher, D. (Munich, Tech. U.) ; Orlandi, R. (JAEA, Ibaraki ; Paisley U.) ; Pakarinen, J. (CERN ; Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Petts, A. (Liverpool U.) ; Peura, P. (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Rahkila, P. (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Reiter, P. (Cologne U.) ; Scheck, M. (Liverpool U. ; Paisley U. ; Glasgow U.) ; Seidlitz, M. (Cologne U.) ; Singh, K. (Weizmann Inst.) ; Smith, J.F. (Paisley U.) ; Van de Walle, J. (CERN) ; Van Duppen, P. (Leuven U.) ; Voulot, D. (CERN) ; Wadsworth, R. (York U., England) ; Warr, N. (Cologne U.) ; Wenander, F. (CERN) ; Wimmer, K. (Munich, Tech. U.) ; Wrzosek-Lipska, K. (Leuven U. ; Warsaw U.) ; Zielińska, M. (Warsaw U. ; IRFU, SPhN, Saclay)
Publication	2015-06-22
Imprint	11 Mar 2015
Number of pages	11
Note	Comments: 12 pages, 14 figures 12 pages, 14 figures
In:	Phys. Rev. C 91 (2015) 064313
DOI	10.1103/PhysRevC.91.064313
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE
Abstract	Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around $Z=82$ and the neutron mid-shell at $N=104$. Purpose: Evidence for shape coexistence has been inferred from $\alpha$-decay measurements, laser spectroscopy and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of $^{202}$Rn and $^{204}$Rn were studied by means of low-energy Coulomb excitation at the REX-ISOLDE facility in CERN. Results: The electric-quadrupole ($E2$) matrix element connecting the ground state and first-excited $2^{+}_{1}$ state was extracted for both $^{202}$Rn and $^{204}$Rn, corresponding to ${B(E2;2^{+}_{1} \to 2^{+}_{1})=29^{+8}_{-8}}$ W.u. and $43^{+17}_{-12}$ W.u., respectively. Additionally, $E2$ matrix elements connecting the $2^{+}_{1}$ state with the $4^{+}_{1}$ and $2^{+}_{2}$ states were determined in $^{202}$Rn. No excited $0^{+}$ states were observed in the current data set, possibly due to a limited population of second-order processes at the currently-available beam energies. Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
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