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Dag Hanstorp Photo detachment of negative ions at ISOLDE: Towards measuring the Electron Affinities of Radioactive Elements S. Rothe, B. Marsh, R.E. Rossel, V. Fedosseev, M. Veinhard , T. Kron, D. Hanstorp, J. Welander, K. Wendt A. Ringvall-Moberg, Y. Liu, T. Day Goodacre, R. Heinke and J. Sundberg ISOLDE workshop and users meeting 2-4 December 2015 Long range forces in atomic systems Coulomb force ~ 1 r Polarisation ~ Penetration ~ 1 r4 1 er Properties of Negative Ions • Small Electron affinities (EA) (appr. 1 eV) Energy • Few (if any) excited states • Optically allowed transitions only observed in Os- , Ce- and La• La- is a good candidate for laser cooling EA sympathetic cooling of antiprotons X- X Why is the sun yellow? Blackbody radiation At T = 5780 K Fusion reactions require T = 100 MK Energy Ivanov VK RADIATION PHYSICS AND CHEMISTRY 70 (1-3): 345-370 MAY-JUN 2004 0,75 eV H- H (Wildt, R. APJ, (1941), 93, 502 ) Targeted Alpha Therapy (TAT) cancer cells a - range Target Carrier Receptor Antibody Immunology Structural biology 211At particularly suitable isotope • 7 h lifetime • No long lived daughters • Non-toxic daughters • Suitable a energy Coordination chemistry Linker Radioactive payload Nuclear physics and radiochemistry Astatine • Least abundant element on earth • 70 mg in the crust of the earth (1 atom per 100 kg mass) • Small knowledge about chemical and physical properties • Behaves sometimes like a metalloid sometimes like halogen - a chemical hybrid Motivation for EA measurement of At and Po Astatine • EA equally important as the IP determine electronegativity nature of chemical bonds • Important for computer simulations for binding of At to receptor • No experimental value for EA(At) yet PHYSICAL REVIEW A 91, 020501(R) (2015) • Scattering of theoretical predictions ~1 eV • Po is considered important component of the natural radiation affecting humans • Physico-chemical properties need to be understood to develop decorporation treatments electron Affinity (eV) Pollonium F Cl Br I 3 PHYSICAL REVIEW A 91, 020501(R) (2015) At S 2 expt. 4c+CCSD(T)+breit+QED MCDF+empirical DK6+DFT O Se Te Po 117 Lv 1 20 40 60 80 100 120 Atomic number Letter of Intent (LOI) INTC-I-148 https://cds.cern.ch/record/1603086/files/INTC-I-148.pdf Collinear photodetachment spectroscopy P- + hn P + eEnergy 3P 0 3P 1 3P 2 Wigner law: s= k (E-E0) l+1/2 P- P GANDALPH Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment I- ITO covered glass e- For each laserpuls: Signal: 0.01 atom Background: 1014 photons Drawing: Annie Ringvall -Moberg GANDALPH Built in the spring 2015 at University of Gothenburg using existing equipment Moved to ISOLDE, June 2015 Installed an put into operation at GLM full control of system Laser transport from RILIS Run HRS in positive mode in parallel Photodetachment of I-, July 2015 RESULTS: Photodetachment of I460 pA of 127I measured on GPS FC.490 28pA Low 10-8 mbar vacuum through ~ 8% transmission to the neutral detector Photodetachment signal of IThreshold still measurable at very low ion rates (<1 pA, FC noise) < 1pA Everyone has been young I was young in 1985 Göran Andersson (one of the founders of ISOLDE) retired and was succeeded by Björn Jonson Björn gave me the isotope separator LILLJON I could start investigating negative ions Summary GANDALPH shown to work Full proposal will be submitted 2016 Looking forward to future ISOLDE user meetings when the EA of At- and Po- will be presented! Thanks to staff at ISOLDE for support! Thank you for your attention!