I. I.4. T HE R EGION A=100, N=60 N E U T R O N S PHERICAL - LIKE W ELL D EFORMED Neutron Rich side What are the origins of the development of deformation? 15 TH -17 TH D ECEMBER 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 2 N=60 Z=37

I. II.1 I NTRODUCTION : THE REGION AROUND A=100, N=60 Mass and charge-radii measurements: shape changes for the ground states at N = 60  Strong tool of investigation. Limits: Mo and Kr isotopic chains? NO onset of deformation for the ground states in Kr (Z = 36). Necessity to clarify the Kr case appeared  Coulomb excitation 94,96 Kr: Smooth appearance of deformation T HE NEUTRON CONTRIBUTION – M ASS AND CHARGE RADII MEASUREMENTS First clue of the onset of deformation Rb isotopic chain Important development of deformation, adding one proton compared to the Kr isotopic chain. S. Naimi et al., Phys. Rev. Lett. 105, (2010) ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 3 15 TH -17 TH D ECEMBER 2014 M. Albers et al., PRL 109, (2012)

I. II.3 T HE P ROTON C ONTRIBUTION Sudden increase of the quadrupole moment at N=60. Magnetic moment measurement of 97 Rb 3/2 + [431] favored but the 3/2 - [301] not excluded Experiment more sensitive requested  Coulomb Excitation R B ISOTOPIC CHAIN CASE Proton side Rb isotopic chain Corner of the onset of deformation  gain more info. on the deformation by adding few nucleons C. Thibault et al., Phys. Rev. C23, 2720 (1981) M.A.C Hotchkiset al., Nucl. Phys. A530, p.111 (1991) ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 4 15 TH -17 TH D ECEMBER 2014 Sudden increase of deformation 95 Rb 93 Rb 97 Rb Nilsson Diagram (Proton) C. Thibault et al, PRC23 (1981) 2720

I. IV. T HE E XPERIMENTAL S ETUP Secondary target 2.1 mg/cm 2 8 clus. x 3 crys. x 6 seg. 16 a. x 12 s. x 4 quad. 60 Ni  -rays emitted in-flight ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 5 15 TH -17 TH D ECEMBER 2014 MINIBALL Gamma-ray detection array Postaccelerated Beam from 2.9 MeV/u CD detector Particle detection setup With: REX-ISOLDE, UCx target, Surface ionization pps beams (10 3 for 99 Rb) De-excitation  -rays measured in coincidence with scattered particles (Rb and Ni) High granularity and energy resolution  Doppler correction

I. V. A NALYSIS AND R ESULTS : Gamma-Gamma Matrix ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 6 Same analysis performed for each isotopes: Prompt-random DC single spectra γ -γ coincidences Level scheme 93 Rb validation case 95 Rb: similar structure (sperical-like) 15 TH -17 TH D ECEMBER 2014 Compton Suppression

I. V. R ESULTS : 97,99 Rb (unknown) ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 7 15 TH -17 TH D ECEMBER 2014

I. V. R ESULTS : GOSIA [*] Matrix elements ~ 1.7 eb Intensities Level scheme All nuclear properties known (lifetimes, quadrupole moment, …) Extraction of transitions strengths GOSIA: χ2 Minimization of the matrix elements of the EM multipole operator  Reproduction of exp. intensities [*]: T. Czosnyka, D. Cline, and C.Y. Wu. Bull. Am. Phys. Soc., 28:745, and A. Winther and J. de Boer, Coulomb Excitation, (Academic, New York, 1965) Similar matrix elements ~ 0.30 eb Matrix Elements, e.g.: ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 8 15 TH -17 TH D ECEMBER 2014 M. Zielinska, private communication, 2014

I. VI. D ISCUSSION ON 97 R B 3/2+[431] K(1) = 3/2, Qo= 2.90, gr = 0.30 |gk-gr|=1.410 F. Kondev, private communication, 2013 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 9 3/2+[431] configuration more probable for the ground state in 97 Rb M. Zielinska, private communication, TH -17 TH D ECEMBER 2014 Nilsson Diagram (Proton) 3/2-[301] K(1) = 3/2, Qo= 2.90, gr = 0.30 |gk-gr|=1.610

I. VII. C ONCLUSION  Coulomb Excitation : independent and complementary information to other approaches  First unambiguous identification of excited states in 97 Rb and 99 Rb.  Different nuclear structures at low energy in 93,95 Rb ≠ 97,99 Rb. Identification of the orbital ( 97,99 Rb) on top of which the g.s. rotational band is built, (π3/2 + [431]). The proton orbital is driving to the deformation. The onset of deformation and Rb isotopic chain Perspectives and Outlooks  Additional experimental sensitivity (e.g. polarized beams?)  Possible lifetime measurement – verification of the model assumptions used in Coulex analysis ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 11 C OLLABORATORS G. Georgiev 1, D. Balabanski 2, G. Simpson 3, J.M. Daugas 4, A. Blazhev 5, N. Bree 6, S. Das Gupsta 7, J. Diriken 6, L. Gaffney 8, K. Geibel 5, K. Hadynska-Klek 9, F. Kondev 10, T. Kroell 11, B. Lannoo 6, P. Morel 4, P. Napiorkowski 9, J. Pakarinen 12, P. Reiter 5, M. Scheck 11, M. Seidlitz 5, B. Siebeck 5, A. Stuchbery 14, H. Törnqvist 12 N. Warr 6, F. Wenander 12, M. Zielinska 9,14 and REX-ISOLDE and Miniball collaborators 1.CSNSM, CNRS/IN2P3; Université Paris-Sud 11, UMR8609, F ORSAY-Campus, France 2.Inst. for Nuclear Research and Nuclear Engineering-INRNE, Sofia, Bulgaria 3.LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, INPG, F Grenoble Cedex, France 4.CEA, DAM, DIF, F Arpajon Cedex, France 5.Institute for Nuclear Physics, Cologne, Germany 6.IKS, KU Leuven, Belgium 7.Dipartimento di Fisica, Universita di Camerino, I Camerino, Italy 8.Olive Lodge Laboratory, University of Liverpool, Liverpool, UK 9.Heavy Ion Laboratory, Warsaw University, Warsaw, Poland 10.Argonne National Laboratory, Argonne, Illinois 60439, USA 11.Technische Universitat Darmstadt, Darmstadt, Germany 12.ISOLDE, CERN, Geneva, Switzerland 13.Department of Nuclear Physics, ANU, Canberra, Australia 14.CEA Saclay, Gif -sur-Yvette, France GOSIA 15 TH -17 TH D ECEMBER 2014

ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

g K -g R ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014 [25] A. Bohr and B. R. Mottelson. Nuclear Structure, volume Vol.I Vol. II. W.A. Benjamin, New York, [36] J.B. Fitzgerald et al., Rotational Bands in the Mass 100 Region. Nuclear Physics, A(530):p. 111–134, 1991.

I. II. T HE C OULOMB E XCITATION K. Alder et al., RMP 28 (56) 432  ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Rotational bands: direct proof of deformation ILL and RIKEN Experiments:  76.5 keV, isomeric state (5-6 µs) keV: different K band QPRM: well reproduced  prediction of 2 quasi-particles excitations G. Simpson, private communication, 2012 I. VI. D ISCUSSION 97 Rb isotope QPRM calculations M.A.C Hotchkiset al., Nucl. Phys. A530, p.111 (1991) Similar structure ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

GOSIA ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. V. R ESULTS : 97 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. V. R ESULTS : 99 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) No target excitation ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Compton suppression ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Time Structure ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

EBIS Extraction ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Efficiency ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. II.3 E XCITED S TRUCTURE ? R B ISOTOPIC CHAIN CASE – O UR K NOWLEDGE B EFORE isomeric and  -decays.: 93,95 Rb Unknown excited structure for 97 Rb – 99 Rb 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 23

I. IV. T HE E XPERIMENTAL S ETUP 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 24

I. IV. T HE E XPERIMENTAL S ETUP M INIBALL REX-LINAC REX-TRAP REX-EBIS 300 kev/u - 3 MeV/u 1+ N+ 60 keV/u  -NMR 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 25

I. II.2 T HE N EUTRON C ONTRIBUTION T HE NEUTRON CONTRIBUTION – N ILSSON O RBITALS AND D EFORMATION Sr and Zr isotopic chain Strongest development of deformation Where is the limits of the onset of deformation? W. Urban et al., Eur. Phys. J. A22, 241 Nilsson Diagram for Neutron (region A=100, N=60) M.A.C Hotchkiset al., Nucl. Phys. A530, p.111 (1991) W. Urban et al., Nucl. Phys. A 689, 3, 2001) R OTATIONAL B AND  DEFORMATION Shape Coexistence in 97 Sr 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 26

Even-Even ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Kinematics ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

DC vs Beam energy vs Phi ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. I.3. N UCLEAR S HAPE « Magic » Number: N= 2, 8, 20, 28, 50, 82, 126 Z = 2, 8, 20, 28, 50, 82, 126 Sphere: isotropic distribution of neutrons and protons  few cases Spherical 50 Spin-orbit coupling  « Magic » Numbers ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. I.3. N UCLEAR S HAPE prolate Minimize potential energies  deformation to be more stable Nilsson notation (asymptotic quantum numbers) The introduction of the different corrections from shell to collective models led to remove quasi totally the degeneracies. ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

Nilsson Diagram ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014 Proton Neutron

I. IV. T HE E XPERIMENTAL S ETUP Particle detection Beam from 2.9 MeV/u    CD Detector (16° – 53°) REX beam Secondary target 2.1 mg/cm 2 Doppler Correction  High Granularity 8 clus. x 3 crys. x 6 seg. 16 a. x 12 s. x 4 quad. 60 Ni Precise determination : the energies and angles for the  -rays and scattered particles  -rays emitted in-flight ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE TH -17 TH D ECEMBER 2014

I. V. R ESULTS : 95 Rb case Same analysis performed: Prompt-random DC single spectra γ -γ coincidences Level scheme New transitions discovered Similar structure than 93 Rb  same configuration 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 34

I. V. R ESULTS : 97 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 35

I. V. R ESULTS : 97 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) Gate on 68.1 keV Projection 68.1 keV 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 36

I. V. R ESULTS : 97 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) Projection Gate on 68.1 keV Gate on keV keV 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 37

I. V. R ESULTS : 97 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) Projection Gate on 68.1 keV Gate on keV Gate on keV keV 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 38

I. V. R ESULTS : 99 Rb case (unknown) Gamma-Gamma Matrix Energy (keV) No target excitation 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 39

P ROBLEMS IN C OULEX DATA ANALYSIS 97R B AND SOLUTIONS 15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 40 Cline’s safe Coulex criterion not fullfilled for high CM angles  15% of statistics excluded from the analysis Efficiency of 68-keV line uncertain  Would be a natural choice for normalisation but had to be excluded from this analysis 355-keV transition in both 97 Rb and 97 Sr  Intensity obtained from gamma-gamma coincidences Undetermined problem : 20 gamma-rays, 24 matrix elements (E2 and M1) Courtesy of M. Zielinska

15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 41 Courtesy of M. Zielinska

15 TH -17 TH M ARCH 2014 ISOLDE W ORK S HOP 2014 S OTTY C HRISTOPHE 42 Courtesy of M. Zielinska