Octupole collectivity studied using radioactiveion beams Liam P

Octupole collectivity studied using radioactive-ion beams Liam P. Gaffney Oliver Lodge Laboratory, University of Liverpool, UK Instituut voor Kern- en Stralingsfysica, KU Leuven, Belgium 1

Octupole Collectivity λ = 2. . . Quadrupole λ 2 λ = 3. . . Octupole correlations enhanced at magic numbers: 34, 56, 88, 134 144 Ba 226 Ra 68 Se 90 Se Exotic regions of the Segré chart, so far inaccessible. 148, , 150 Nd Radioactive Ion Beams are the key Schiff moment EDM CP violation Talk by Peter Butler earlier this morning Odd-A 2

Octupole Collectivity 184 Microscopically. . . Intruder orbitals of opposite parity and ∆J, ∆L = 3 close to the Fermi level 134 126 88 82 εF 56 50 220 Rn 34 and 224 Ra lie near Z=88, N=134 28 3 20

Octupole Collectivity Macroscopically. . . Nuclei take on a “pear” shape Reflection asymmetric • β 3 -vibration • Static β 3 -deformation • Rigid β 3 -deformation. . . Signatures. . . Odd-even staggering, negative parity Parity doublets in odd-A nuclei Enhanced E 1 transitions Large E 3 strength → = 4

Octupole Collectivity Z = 88 N = 134 Z = 56 Rn (Z=86)? 5

Radon-220 and Radium-224 220 Rn 224 Ra [ref] J. F. C. Cocks et al. Phys. Rev. Lett. 78 (1997) and Nucl. Phys. A 645 (1999) 6

Coulomb Excitation Projectile (Z 1, A 1) Sommerfeld parameter: θ b v Target (Z 2, A 2) “Safe” Coulex: Reduced matrix elements: 7

Isotope Separation On. Line DEtector RIB EXperiment REX-ISOLDE Radioactive Ion Beam A 1. 4 Ge. V protons from PS Booster DPost-acceleration C Mass separation in HRS Heated tungsten line (Ra) B Plasma ion source (Rn) Ionised atoms diffuse out of target 8 UCx

MINIBALL @ REX-ISOLDE 220 Rn/224 Ra beam @ ~2. 83 A. Me. V Coulex target ~2 mg/cm 2 9

MINIBALL • Particle ID in a Double -Sided Si Strip Detector. • Event by event Doppler correction. • 17˚ < θlab < 54˚ • Array of HPGe of 8 triple clusters • 6 -fold segmentation for positioning • ε > 7% for 1. 3 Me. V γ-rays 10

Particle-gamma coincidences Prompt Random Normalisation = tprompt trandom 11

Analysis - 224 Ra: 60 Ni target - 2. 1 mg/cm 2 120 Sn target - 2. 0 mg/cm 2 12 Ni/Sn

Analysis - 220 Rn: 60 Ni Ni/Sn target - 2. 1 mg/cm 2 120 Sn target - 2. 3 mg/cm 2 13

Analysis - 220 Rn γ-γ γ(697 ke. V) 14

Analysis - 220 Rn: High Co. M θ Low Co. M θ 15 High/Low θ

Analysis - 224 Ra Gosia 16 free matrix elements + 6 normalisation factors “Experiment” Number and type of data Multi-nucleon transfer[1, 2] 226 Ra(58 Ni, 60 Ni)224 Ra 232 Th(136 Xe, 128 Te)224 Ra Alpha, alpha-prime[3] 226 Ra(α, α’ 2 n)224 Ra Alpha(beta)-decay[4] 228 Th(224 Fr) → α(β) Branching ratios (1 -, 3 -, 5 -, 7 -, 2+γ) Delayed-coincidence[5, 6] Lifetimes (2+, 4+) Cd/Sn high Co. M range 23. 9˚ < θlab < 40. 3˚ γ-ray yield Ni high Co. M range 23. 1˚ < θlab < 39. 9˚ γ-ray yield Cd/Sn low Co. M range 40. 3˚ < θlab < 54. 3˚ γ-ray yield Ni low Co. M range 39. 3˚ < θlab < 53. 2˚ γ-ray yield χ2 = 0. 55 -- 2 -- 8 + 7 -- 10 -- 8 + 8 -- 7 Total 55 data points 16 [1] Poynter et al. , Phys. Lett. B 232, 447 (1989) [2] J. F. C. Cocks et al. , Nucl. Phys. A 645, 61 (1999) [3] Marten-Tölle et al. , Z. Phys. A 336, 27 (1990) [4] W. Kurcewicz, et al. , Nucl. Phys. A 289 (1977) [5] W. R. Neal and H. W. Kraner, Phys. Rev. 137, B 1164 (1965) [6] H. Ton et al. , Nucl. Phys. A 155, 235 (1970)

A Em w ai ba ti rg ng oe pu d b by lic Jo atio ur n na l Results - 224 Ra • Consistent with rotational model • Unstretched E 3 matrix elements are non -zero. Rot-vib model predicts these vanish • Coupled with level energy data, we observe a static octupole deformation in 224 Ra 531 - 4+ 2+ 17 0+ 3ℏ phonon

Analysis - 220 Rn Gosia 15 free matrix elements + 6 normalisation factors “Experiment” Number and type of data Multi-nucleon transfer[1, 2] 226 Ra(58 Ni, 60 Ni)224 Ra 232 Th(136 Xe, 128 Te)224 Ra Alpha, alpha-prime[3] 226 Ra(α, α’ 2 n)224 Ra Alpha(beta)-decay[4] 228 Th(224 Fr) → α(β) Branching ratios (1 -, 5 -, 7 -) Delayed-coincidence[5, 6] Lifetimes (2+) Cd/Sn/Ni high Co. M range 22. 1˚ < θlab < 37. 8˚ γ-ray yield Cd/Sn/Ni low Co. M range 37. 9˚ < θlab < 51. 8˚ γ-ray yield χ2 = 0. 86 -- 3 -- 1 -- 2 + 8 + 5 Total 34 data points 18 [1] Poynter et al. , Phys. Lett. B 232, 447 (1989) [2] J. F. C. Cocks et al. , Nucl. Phys. A 645, 61 (1999) [3] Marten-Tölle et al. , Z. Phys. A 336, 27 (1990) [4] W. Kurcewicz, et al. , Nucl. Phys. A 289 (1977) [5] W. R. Neal and H. W. Kraner, Phys. Rev. 137, B 1164 (1965) [6] H. Ton et al. , Nucl. Phys. A 155, 235 (1970)

Results - 220 Rn • Consistent with rotational model. • No information on unstretched E 3. • Larger data set required to determine if <1 -||E 3||2+> or <1 -||E 3||4+> vanish. Aw Em a ba itin rg g oe pu d bli by ca Jo tio ur n na l • Not definitive determination of collective mode, dynamic (vibrational) or static (rotational) from Q 3 alone. • δE and Δix implies a coupling of an octupole phonon to the even-spin rotational band. • Magnitude of Q 3 consistent with dynamic picture, similar to Q 3(208 Pb) and Q 3(232 Th) • Dynamic collectivity in 220 Rn 19

220 Rn - Vibrational? 20

Discussion and Interpretation 8 -8 21

Discussion and Interpretation 22

Comparison to theory Awaiting publication Embargoed by Journal • Cluster model [1] - Misses small Q 1 - Q 2 is consistently too low - Q 3 trend not observed Q 2 • Mean field, HFB with D 1 S or D 1 M [2] - Predicts cancelation of Q 1 - Differences in Q 3 predictions [1] Shneidman, et al. (2003). Phys. Rev. C, 67(1), 14313 [2] Robledo, L. M. , & Bertsch, G. F. (2011). Phys. Rev. C, 84(5), 54302. Q 1 Q 3 23

Summary & Outlook • Demonstrated sensitivity and ability to measure E 3 matrix elements with Radioactive Ion Beams (RIBs). • B(E 3; 3 - -> 0+) measured for the first time in Rn and only second measurement in Ra, both to ~10% precision. • Experimental values rule out trend of cluster models. • Exposes detailed differences in parameterisations of mean field calculations. • Proposal for measurements in 222, 226, 228 Ra and Ba region. • Odd-mass nuclei key to atomic EDM measurements See talk by George O’Neill at 15. 45 today 24

Collaborators T. E. Cocolios, J. Pakarinen, J. Cederkall, D. Voulot, F. Wernander Th. Kröll, S. Bönig, C. Bauer, M. von Schmid B. Bastin T. Grahn, A. Herzan A. Blazhev, M. Seidlitz, N. Warr, M. Albers, M. Pfeiffer, D. Radeck M. Rudigier, P. Thöle P. van Duppen, N. Bree, J. Diriken, N. Kesteloot S. Sambi, K. Reynders L. P. Gaffney, P. A. Butler, M. Scheck, D. T. Joss, S. V. Rigby E. Kwan T. Chupp D. Cline, C. Y. Wu M. Zielinska, P. Napiorkowski, M. Kowalczyk D. G. Jenkins CERN-ISOLDE, Switzerland TU Darmstadt, Germany and the REX-ISOLDE and MINIBALL collaborations Ganil, France University of Jyväskylä, Finland University of Köln, Germany Thank you! KU Leuven, Belgium University of Liverpool, UK Lawrence Livermore Laboratory, US University of Michigan, US 25

Aside - Protons off. . . ! • Evidence of rapid exponential decay in beam rate after protons cease • Comparison of direct production vs. alpha decay of parent (T 1/2 = 3. 66 days) 26

Radon-220 and Radium-224 220 Rn 224 Ra 27

Simulation - 28 224 Ra

Simulation - 29 224 Ra

Gosia Analysis Measured E 3 matrix elements [e·fm 3] Stretched: Un-stretched: Measured E 2 matrix elements [e·fm 2] Transitional: Diagonal: [Ref] H. J. Wollersheim et al. , Nucl. Phys. A 556, 261 (1993) 30

Gosia Analysis 31

Discussion and Interpretation - 32 224 Ra