Detection of X rays in the Neutron-Deficient Polonium Coulomb Excitation Experiments Nele Kesteloot IKS KU Leuven SCK CEN

Outline ●The polonium isotopes ●Experimental campaign ●X rays ●Overview ●Origin ●K-vacancy creation in collision ●Corrections ●Normalization ● 206 Po ● 188 Hg ●E0 transitions ●Other pitfalls ●Outlook 25th of October 2013Miniball Workshop CERN2

25th of October 2013Miniball Workshop CERN3 The polonium isotopes Experimental campaignX raysOutlook Generalized seniority Shape coexistence T.E. Cocolios et al. PRL 106: (2011) N = 116 M.D. Seliverstov et al., in preparation Change in nuclear structure Transition expected around 200 Po R. Julin et al JPG 27:R109 (2001) A.M. Oros et al NPA 645:107 (1999) (π1h9/2) 2 Other pitfalls

Experimental campaign 25th of October 2013Miniball Workshop CERN4 The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – Overview 25th of October 2013Miniball Workshop CERN5 196 Po on 104 Pd 198 Po on 94 Mo 200 Po on 104 Pd 202 Po on 104 Pd 202 Po on 94 Mo 206 Po on 104 Pd The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – Origin 25th of October 2013Miniball Workshop CERN6 Conversion of observed 200 Po gamma rays X rays Atomic production of K vacancy in ion-atom collision Po E0 transition  The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

●Ion-atom collision gives rise to production of K vacancy ●Theoretical formula ●Scale proton-induced cross section to heavy projectile ●Change reference frame ●K-vacancy in projectile ●Energy per nucleon remains unaltered ●Very sensitive to beam energy ●Take energy loss in target into account X rays – K-vacancy creation in collision 25th of October 2013Miniball Workshop CERN7 J.D. Garcia et al, RMP 45 No 2 (1973) 111 The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – Corrections ●Empirical correction 25th of October 2013Miniball Workshop CERN8 σ exp / σ th 132 Xe projectile on target with Z protons 2.4 MeV/u 3.6 MeV/u 4.7 MeV/u 5.9 MeV/u S exp = 0.070(15) Z σ exp / σ th Z 208 Pb projectile on target with Z protons The polonium isotopesExperimental campaignX raysOutlookOther pitfalls H.-H. Behncke et al., Z. Phys. A 289 (1979) 333

X rays – Corrections ●Geometrical correction 25th of October 2013Miniball Workshop CERN9 Detection range in center-of-mass frame S det = (18) The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – Normalization 25th of October 2013Miniball Workshop CERN10 ●No observed low-lying excited 0 + states ●X rays ●Conversion of observed gamma lines ●K-vacancy creation in ion-atom collision 206 Po on 104 Pd Po Po (3,4) Po on 104 Pd The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – Normalization ●Compare to X rays in Hg coulex ●Scale to 188 Hg 25th of October 2013Miniball Workshop CERN11 IsotopeTargetExpectedObservedRatio 202 Po 104 Pd82(16)250(66)3.2(10) 202 Po 94 Mo59(14)189(39)3.0(10) 206 Po 104 Pd113(20)296(135)2.6(13) Weighted average: 2.82(49) IsotopeTargetExpectedObservedRatio 188 Hg 114 Cd709(180)459(86)0.65(20) 188 Hg 107 Ag98(25)49(25)0.50(28) 188 Hg 120 Sn1062(264)535(91)0.50(15) Weighted average: 0.55(11) The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – E0 transitions in Po 25th of October 2013Miniball Workshop CERN12 The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

X rays – E0 transitions in Hg 25th of October 2013Miniball Workshop CERN Hg 114 Cd 107 Ag 120 Sn 186 Hg 114 Cd 107 Ag 120 Sn 184 Hg 112 Cd 107 Ag 120 Sn 182 Hg 112 Cd Observed X rays / Expected X rays (%) The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

●Gamma ray detection efficiency ●Rapidly varying at low energies ●Need for good efficiency calibration curve ● 152 Eu and 133 Ba sources ●Coincidence method ●Random subtraction ●Big amount of randoms at low energies ●Number of X rays very sensitive to p/r scaling factor! ●Correct propagation of error bars is crucial ●Fit of X-ray peaks 25th of October 2013Miniball Workshop CERN14 The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

●Multiple origins for X rays in coulex data ●Conversion of gamma lines ●E0 transition between two 0 + states ●K-vacancy creation in ion-atom collision ●Theory as qualitative basis ● 206 Po/ 188 Hg as normalization ●Correct assessment of X rays is crucial ●Number of E0 transitions determines population of state ●Influence on extracted matrix elements ●Normalization factors in other data sets ●Pb coulex ●Rn coulex 25th of October 2013Miniball Workshop CERN15 Conclusion and Outlook The polonium isotopesExperimental campaignX raysOutlookOther pitfalls

25th of October 2013Miniball Workshop CERN16 B. Bastin E. Clement N. Lecesne N. Bree H. De Witte J. Diriken L. Gaffney M. Huyse P. Van Duppen K. Wrzosek-Lipska V. Fedosseev B. Marsh E. Piselli E. Rapisarda M. Seliverstov T. Stora D. Voulot F. Wenander T. Grahn J. Konki J. Pakarinen P. Reiter B. Siebeck N. Warr T. Kröll, Technische Universität Darmstadt P. Butler, University of Liverpool M. Scheck, University of West Scotland, Paisley M. Zielinska, CEA Saclay Thank you!

25th of October 2013Miniball Workshop CERN17 γγ coincidences in 198 Po Po Gate on 605 keV Gamma energy (keV) Number of counts / 2 keV

25th of October 2013Miniball Workshop CERN18 γγ coincidences in 196 Po Po Gate on 463 keV