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

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

ISOLDE Decay Station http://isolde-ids.web.cern.ch/isolde-ids/#setup

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

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 2016 - 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

A “Successful” Test at IDS The purpose of the test was to obtain 87 232 𝐹𝑟 145 The unexpected result 213Ra19F (molecular beam) 1/2- 88 213 𝑅𝑎 86 209 𝑅𝑛 214.7 5/2 - 1/2 - 3/2 - 110.1 𝛼 80% 45% 49% 6% 𝛽+/EC 20% 87 213 𝐹𝑟 498 (7/2 -) 9/2 - 110keV 209Rn 498keV 213Fr X-rays 213Fr 227 400 215keV 209Rn 733 942 908 1128 1142 1300 317

213Fr – Physics Case 87 213 𝐹𝑟 126 213Ra 213Fr Shell Model calculations E. Teruya et. al. 10.1103/PhysRevC.93.064327 87 213 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 1/2- 2.73(5) m 213Ra 9/2- 34.6(3) s 213Fr β+/EC ~20% low spin excited states

213Fr – Previous Experimental Results -Low Spin States- Pragati et al. Decay of the N=126, 213Fr nucleus Phys. Rev. C 94 (2016) 064316 M. Guttormsen et al. A superconducting electron spectrometer Nucl. Instrum. Meth. In Phys. Res. 227 (1984) 489-498 Conversion Electrons R. A. Meyer et al. HMI-393, ISSN 0440-0836 (1983) 86 Internal report The evolution of single particle state in the odd-even isotonic 213Fr chain

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

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 2949.5-keV in 213Fr We expect from the selection rules that the levels with high feeding to have spins Jπ=1/2- or 3/2-

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, 054310 EC/

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

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) 489-498 Pragati et al. Decay of the N=126, 213Fr nucleus Phys. Rev. C 94 (2016) 064316

Thank you for attention!