Maria Kmiecik, Giovanna Benzoni, Daisuke Suzuki COULOMB EXCITATION TAGGED BY BETA DECAY The Onset of Deformation in Neutron-Rich Yttrium Isotopes SPES LoI Maria Kmiecik, Giovanna Benzoni, Daisuke Suzuki

for the PARIS collaboration IFJ PAN Krakow: M. Kmiecik, P. Bednarczyk, M. Ciemała, A. Czermak, B. Fornal, J. Grębosz, A. Maj, K. Mazurek, B. Wasilewska, M. Krzysiek, M. Ziębliński et al. HIL, Warsaw University: P.J. Napiorkowski, M. Palacz, J. Srebrny et al. Milano University: G. Benzoni, A. Bracco, F. Camera, S. Leoni, B. Million, A.I. Morales, O. Wieland et al. IPN Orsay: D. Suzuki, F. Azaiez, D. Beaumel, S. Franchoo, I. Matea, I. Stefan et al. CSNSM: G. Georgiev et al. LNL Legnaro: G. de Angelis, J.J. Valiente-Dobon, D. Napoli et al. GANIL: O. Sorlin, G. de France, E. Clement, Ch. Schmitt et al. GSI: M. Górska, J. Gerl et al. University of Tokyo: M. Niikura for the PARIS collaboration

Onset of deformation in Y isotopes nuclear charge radii differences and electric quadrupole moments in ground states of 86–90,92–102Y and isomeric states of 87–90,93,96,97,98Y studied using laser spectroscopy 98Y isomeric state The experimental charge radii for Y isotopes compared to estimates that were obtained by assuming static β2 deformation alone. The two dashed lines correspond to calculations made assuming deformation parameters βrms = 0 and 0.43 N  60 – prolate 98Y ground state Yttrium isotopes: change of deformation possible shape coexistence in many isotopes long-living isomeric states 50N<60 – oblate B. Cheal et al., Physics Letters B 645, 133 (2007)

98Y Different decay chains following b decay of isomer and g.s b-delayed g from isomer: 620.5 (27.6%) 647.6 (23%) 1801 (17%) 1223 (35%) not well defined structure of 98Y g.s. confirmed as 0-; spin of isomeric state is I=4 or I=5, parity non defined b-delayed g from g.s.: 269 (21%) 1223 (100%) 1590 (41%) 2941 (48%) 3310 (20%) 4450 (28%) Different decay chains following b decay of isomer and g.s K. Sistemich et al., Z. Physik A 281, 169 (1977).

b-decay tagged Coulomb excitation We propose to measure deformation of 98Y nuclei in both the ground state or in excited isomeric state using gamma-rays from Coulomb excitations (Coulex) tagged by recoil – beta-decay correlations 98Y Different g-cascades after b-decays allowing for unique selection of CoulEx on g.s. and isomeric state feasibility study to define and construct the high efficiency setup for measurements of Coulomb excitations on ground and beta-decaying isomeric states of radioactive beams of SPES

98Y SPES beam Intensity: 104-105 pps A/q = 7 - feasible

Experimental setup scheme PARIS 2 / HECTOR+ (delayed gamma-rays) need to develop high efficiency setup GALILEO 2 (prompt gamma-rays) beam DSSSD pixels Log pre-amps (For HI and b) (ie. used in RISING - 2048 pixels) 98Y (cocktail of g.s. and isomers) 105 pps E = 4 MeV/A distance from target ca. 15 - 20 cm additional gamma ray detector - to increase efficiency target angle and distance from target of DSSSD should be optimized for Coulex taking into account shielding 208Pb 0.5mg/cm2 detailed calculations needed

trigger and rates How to correlate events? Prompt gamma ray + ion stopped in DSSSD – time stamped b-decay + delayed gamma - time stamped 98Y @ 4 AMeV Intensity 105 pps Target: 208Pb 0.5mg/cm2 Coulomb excitation estimated rates (GOSIA) g. s. transition energy counts 1- → 0- 119 keV 3600/h isomer: 5- → 4- 176 keV 53000/h GALILEO 2 efficiency: 4% measured rates: g. s. 2/min (0.04/s) isomer: 35/min (0.6/s) max rate of implanted ions in DSSSD from the reaction 1/s PARIS 2 efficiency: 15-20%

Simulated energy spectrum b-delayed g from isomer: 620.5 (27.6%) 647.6 (23%) 652 1801 (17%) 1223 (35%) Simulated energy spectrum for PARIS 2 array simulations by Michał Ciemała b-delayed g from g. s.: 213 269 (21%) 521 836 890 1223 (100%) 1590 (41%) 1744 (15%) 2420 (13%) 2941 (48%) 3310 (20%) 4450 (28%) isomer g.s. gates on 98Zr transitions - choosing events from Coulex on ground or isomeric states in 98Y – B(E2)

Conclusions we propose feasibility study of deformation of radioactive nuclei produced in both the ground state or in excited isomeric state using beta-decay tagged Coulomb excitation with 98Y beam the development and construction of high-efficiency experimental set-up needed SPES beams of radioactive nuclei are good for such investigations