Speaker
Dr
Andrew Robinson
(University of York)
Description
One of the remarkable properties of the nucleus is its ability to minimise its energy by adopting different deformed nuclear shapes. In some cases, this can lead to competing minima very close together. This phenomena has been widely tracked through the neutron-deficient lead, mercury and platinum isotopes, where the shape coexistence has been discussed in terms of intruder states based on proton particle-hole excitations across the Z=82 shell gap [1].
Particle-hole intruder states similar to those found in the light lead nuclei are expected to be present in nuclei above the Z=82 closure, for example 4p2h and 6p2h configurations in the polonium and radon isotopes. Such phenomena have been most extensively investigated in the light polonium nuclei, where low-lying excited 0+ states have been observed following the alpha decay of 200,202Rn [2] and the beta decay of 200,202At [3]. Energy systematics and branching ratios have been used to interpret such states as intruders, which appear to mix with the spherical ground-state configurations in isotopes lighter than 200Po [4]. Candidates have been found in 202,204Rn for deformed intruder states [5], which coexist with the spherical ground-state shape however this assignment can be no more than speculation given the absence of any detailed experimental information such as electromagnetic matrix elements.
Coulomb excitation (Coulex) with radioactive beams has shown to be a highly successful method for establishing the evolution of nuclear shape. Notable examples of this class of measurement include the Coulex of 74,76Kr at SPIRAL [7] and 70Se at REX-ISOLDE [7]. Recently a number of experiments have been performed at REX-ISOLDE studying shape coexistence in the light mercury isotopes with Coulex. These highly successful measurements have recently been extended to study shape coexistence in even heavier nuclei.
Preliminary results from our recent Coulex experiment studying shape coexistence in the light radon isotopes, 202Rn and 204Rn, will be presented.
[1] J.L. Wood et al., Phys. Rep. 215, 101 (1992)
[2] J. Wauters et al., Z. Phys. A 344, 29 (1992); Phys. Rev. Lett. 72, 1329 (1994)
[3] N. Bijnens et al., Phys. Rev. Lett, 75, 4571 (1995); Phys. Rev. C 58, 754 (1998)
[4] R. Julin, J. Phys. G 27, R109 (2001)
[5] D.J. Dobson et al., Phys. Rev. C 66, 064321 (2002)
[6] E. Clement et al., Phys.Rev. C 75, 054313 (2007)
[7] A.M. Hurst et al., Phys. Rev. Lett. 98, 072501 (2007)
Author
Dr
Andrew Robinson
(University of York)
Co-authors
Dr
Alick Deacon
(University of Manchester)
Mr
Andreas Ekstrom
(Lund Univesity)
Dr
Andrei Andreyev
(IKS K.U. Leuven)
Mr
Andrew Petts
(University of Liverpool)
Dr
Baharak Hadinia
(University of the West of Scotland)
Dr
David Jenkins
(University of York)
Douglas DiJulio
(Lund Univesity)
Dr
Janne Pakarin
(University of Liverpool)
Dr
Jarno Van de Walle
(CERN)
Dr
John Smith
(University of the West of Scotland)
Kuljeet Singh
(Weizmann Insitute of Science)
Dr
Marcus Scheck
(University of Liverpool)
Prof.
Micheal Hass
(Weizmann Insitute of Science)
Miniball Collaboration
(Miniball)
Mr
Nick Bree
(IKS K.U. Leuven)
Dr
Panu Rahkila
(University of Jyvaskyla)
Prof.
Peter Buttler
(University of Liverpool)
Dr
Riccardo Orlandi
(University of the West of Scotland)
Prof.
Sean Freeman
(University of Manchester)
Mr
Stewart Martin-Haugh
(University of York)
Dr
Tuomas Grahn
(University of Liverpool)
Dr
Vivek Kumar
(Weizmann Insitute of Science)
