1. ISOLDE Workshop and Users Meeting 2017
First Observation of the Low-Spin Structure of 213Fr Populated in the EC/β+ Decay of 213Ra
Cristina Clisu on behalf of the IS608, IDS and Windmill collaboration
ISOLDE Workshop and Users Meeting 2017

2. Content ISOLDE Decay station IS608 The β+/EC decay of 213Ra
The low spin structure of 213Fr
The comparison between experimental results and the theory

3. ISOLDE Decay Station

4. IDS – Particle Spectroscopy Configuration
Set-up:
4 HPGe Clover detectors
4 Si PADs + 2 DSSSDs detectors
The particle detectors are fixed onto a separate printed circuit board that can slide into the main chamber
This is the first time when the tapestation was used together with particle detectors at IDS.
IDS Particle Spectroscopy + Tapestation

5. IS608: Shape-coexistence and shape-evolution studies for bismuth isotopes by insource laser spectroscopy and beta-delayed fission in 188Bi.
Physics:
(1) β-delayed fission (βDF) of two isomeric states in 188Bi (using WINDMILL)
(2) shape-coexistence/ evolution phenomena in Bi isotopic chain by in-source laser spectroscopy measurements of IS and HFS (using IDS)
Spokesperson: A.N. Andreyev (Univ. York)
A. Barzakh (Gatchina)
P. Van Duppen (KUL)
Set-up and Methodology:
UCx Target at GPS
First Windmill-IDS-RILIS Collaboration
Demonstrated unique power of IDS for HFS studies at IDS
188m1,193,193m,195,195m,197,197m,200m2,203m,214,214m,215,215mBi were measured
MR-ToF Measured HFS for Ground state in 215Bi (T1/2=7.7 minutes)
- Hint of T1/2 =30-s Isomer at E*~1.3 MeV is hidden below,
and much less produced, was not seen at MR-ToF
IDS 2017 – Isolated the isomeric state (~30 s ) by gating on IT cascade

6. A “Successful” Test at IDS
The purpose of the test was to obtain 𝐹𝑟 145
The unexpected result 213Ra19F (molecular beam)
1/2- 𝑅𝑎 𝑅𝑛
214.7
5/2 -
1/2 -
3/2 -
110.1
𝛼 80%
45%
49% 6%
𝛽+/EC 20% 𝐹𝑟
498
(7/2 -)
9/2 -
110keV 209Rn
498keV 213Fr
X-rays 213Fr
227
400
215keV 209Rn
733
942
908
1128
1142
1300
317

7. 213Fr – Physics Case 87 213 𝐹𝑟 126 213Ra 213Fr
Shell Model calculations
E. Teruya et. al /PhysRevC
𝐹𝑟 126
Magic on neutrons N=126
5 valence protons above the last closed shell
In the spherical shell model picture, the lowest excited states are expected to be dominated by the proton excitations above Z=82
The high spin states – well studied in alpha decay
β decay selection rules:
∆J=0,±1
∆π=0
From 1/2- we expect to populate excited states with low spins
1/ (5) m
213Ra
9/ (3) s
213Fr
β+/EC
~20%
low spin excited states

8. 213Fr – Previous Experimental Results -Low Spin States-
Pragati et al. Decay of the N=126, 213Fr nucleus Phys. Rev. C 94 (2016)
M. Guttormsen et al. A superconducting electron spectrometer Nucl. Instrum. Meth. In Phys. Res. 227 (1984)
Conversion Electrons
R. A. Meyer et al. HMI-393, ISSN (1983) 86 Internal report
The evolution of single particle state in the odd-even isotonic 213Fr chain

9. Data Analysis Procedure: Gate 498keV 4 HPGe Clover Detectors
X-rays
400
733
1142
908
498
Gate 498keV
Gate 1142keV
Procedure:
4 HPGe Clover Detectors
γ-γ spectroscopy
The starting point: the already known 498-keV transition and the characteristic X-rays of Francium
The constructed level scheme is based on the γ-γ coincidences using the efficiency curve determined with the 152Eu source
83.2
86.1
97.5
100.3

10. Preliminary Results
EC/ Iβ
Using the intensities of the gamma transitions preliminary values of the β feeding have been estimated
The β-decay of 213Ra predominantly populates the keV in 213Fr
We expect from the selection rules that the levels with high feeding to have spins Jπ=1/2- or 3/2-

11. Theory vs Experiment H. Grawe Shell Model calculations Core : 208Pb
Valence space : π(09/2, 1f7/2, 0i13/2, 2p3/2, 1f5/2, 2p1/2)
Code: NATHAN
Interaction : modified Kuo- Herling
E. Caurier et al Phys. Rev. C 67,
EC/

12. Conclusions
IS608 – The first collaboration between IDS, Windmill and RILIS
During a test we obtained the 213Ra19F molecular beam
213Ra decays into 213Fr by β+/EC
From γ-γ analysis we obtained the low spin level scheme of 213Fr
Shell Model calculations

13. Outlook: Conversion Electron Investigation for 213Fr
The 175-keV, 228-keV, 317-keV, 339-keV, 400-keV, 475-keV, 498-keV transitions in 213Fr are converted.
The conversion coefficient can provide information about the multipolarity of the transitions and the spin and parity of the excited states.
The level scheme can be thus improved by combining information of γ-spectroscopy and conversion electrons.
M. Guttormsen et al. A superconducting electron spectrometer Nucl. Instrum. Meth. In Phys. Res. 227 (1984)
Pragati et al. Decay of the N=126, 213Fr nucleus Phys. Rev. C 94 (2016)

14. Thank you for attention!