1. 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

2. 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

3. 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)

4. 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).

5. 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

6. 98Y SPES beam
Intensity: pps
A/q = 7 - feasible

7. 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 pixels)
98Y
(cocktail of g.s.
and isomers)
105 pps
E = 4 MeV/A
distance from target ca 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

8. trigger and rates How to correlate events?
Prompt gamma ray + ion stopped in DSSSD – time stamped
b-decay + delayed gamma - time stamped
4 AMeV
Intensity 105 pps
Target: 208Pb 0.5mg/cm2
Coulomb excitation estimated rates (GOSIA)
g. s. transition energy counts
1- → keV 3600/h
isomer:
5- → keV /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%

9. 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)

10. 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