1. James Cubiss University of York jgc511@york.ac.uk On behalf of the IS534, Sep 2014 collaboration Hyperfine structure studies of At isotopes using in-source laser spectroscopy at ISOLDE Z=82 N=126

2. University of York, United Kingdom A. N. Andreyev, J. G. Cubiss, B. Whitmore, G. L. Wilson RILIS, CRIS and ISOLDE, Geneva, Switzerland S. Rothe, B. A. Marsh, A. M. Sjodin, V. N. Fedosseev, M. D. Seliverstov, N. Imai, K. Lynch Institut für Physik, Johannes Gutenberg-Universität Mainz, Mainz, Germany S. Raeder, K. D. A. Wendt Instituut voor Kern- en Stralingsfysica, K.U. Leuven, Leuven, Belgium L. Ghys, C. Van Beveren, E. Rapisarda, D. Pauwels, D. Radulov, Yu. Kudryavtsev, M. Huyse, P. Van Duppen Comenius University, Bratislava, Slovakia S. Antalic, Z. Kalaninova, B. Andel PNPI, Gatchina, Russian Federation A. Barzakh, D. V. Fedorov, P. Molkanov University of Manchester, UK I. Straschnov, T. E. Cocolios MR-TOF@ISOLTRAP team: S. Kreim, V. Manea, +... University of Liverpool F. Wearing, A. Gredley Collaborators IS534, Sep 2014 collaboration

3. Previous work on charge radii near Z =82 Pb ISOLDE, PRL98, 112502 (2007) H. De Witte et al. Po ISOLDE,PRL106, 052503 (2011) T. Cocolios et al., 2011: Tl isotopes: IS511 ISOLDE and IRIS(Gatchina) At?

4. IDS NICOLE MINIBALL TAS VITO MR-ToF Windmill COLLAPS CRIS WITCH collections HRS Target GPS ISCOOL ISOLDE hall & RILIS 1.4 GeV Protons From PSB RILIS

5. 205 At Total photon energy cm -1 Ion count intensity a.u. Development of At beams & ionisation scheme

6. B. A. Marsh et al., 20013 EMIS conference, NIM B317, p.550 (2013) WM: A.N. Andreyev et al, Phys. Rev. Lett 105, 252502 (2010) MR-ToF MS: R. N. Wolf et al, NIM, A686, 82 (2012) Our tools for measuring hyperfine splitting (HFS)

7. HFS spectrum, 205At from Faraday cup Fitted using a Voigt profile: - Lorentzian (Laser line shape) - Gaussian (Doppler) “Centre of Gravity ” (CoG) is taken from the HFS fits. Can extract: - magnetic moment - quadrupole moments - nuclear spins - Δδ T ½ = 26.9 m

8. Annular Si Si Pure 60 keV beam from RILIS+ISOLDE C-foils 20 m g/cm 2 Si detectors 60 keV beam from ISOLDE Si Annular Si ff  C-foil LEGe detector A.N. Andreyev et al., PRL 105, 252502 (2010) Setup: Si detectors both sides of the C-foil Simple setup & DAQ: 4 PIPS (1 of them – annular) Large geometrical efficiency (up to 80%) 2 fold fission fragment coincidences ff-gamma coincidences Digital electronics Windmill system at ISOLDE

9. 200At 3 distinguishable peaks from 3 isomers of 200At. Gate on alpha energies to see HFS. 3 isomers of 200At, Windmill No shift in CoG, three isomers have same deformation! R max = the maximum peak rate. NαNα Wavenumber [cm -1 ] 200At 6411 keV, 7+ T ½ = 47 s 6464 keV, 3+ T ½ = 43 s 6536 keV, 10- T ½ = 3.5 s NαNα Energy [keV] 200Po R max ≈ 20 α/s R max ≈ 50 α/s R max ≈ 80 α/s

10. Isomeric shifts and shape coexistence, 197At δ between isomers. Investigating shape coexistence! T ½ = 0.388 s R max ≈ 100 α/s T ½ = 2 s R max ≈ 36α/s

11. Alpha- & beta- decay studies with Windmill, 218At Dedicated decay studies. Can measure: - Alpha- and gamma- decay energies - Branching ratios - Half-lives Secondary confirmation of spin assignments (prompt gammas following β). Develop decay schemes. Free! By-product of HFS studies! 218At T ½ = 1.5 s 218Fr214At T ½ ≈ 1 ms T ½ = 558 ns

12. MR-ToF MS: R. N. Wolf et al, NIM, A686, 82 (2012) The windmill setup depends on decay measurements. No good for long-lived or stable isotopes. Better off counting ions with MR-ToF (Multi Reflection Time of Flight spectrometer)! (Frank Wienholtz, 15.12.2014) MR-ToF at ISOLDE

13. Can also deal with isobaric contamination. MR-ToF – dealing with isobars T ½ = 1.81 h Produce HFS by gating on ToF.

14. Reproducibility with MR-ToF, 203At MR-ToF, on-line analysis, IS534 (2014) T ½ = 7.4 m R max ≈ 60 ions/s

15. Isotopic shift between At isotopes Sample of results. Difference between CoG gives the isotopic shift. From isotopic shift, δ can be calculated. Measuring deformation across the nuclear chart. Results from 2 months ago. Final analysis underway. T½ = 32.3 ms R max ≈ 175 α/s T½ = 7.214 h R max ≈ 20 ions/s T½ = 26.9 ms T½ = 7.03 s R max ≈ 100 α/s T½ = 328 ms R max ≈ 5 α/s

16. Charge radii plot for At – IS534, Sep 2014 N = 126 Spherical region Onset of deformation Possible octupole deformation?

17. Thank you for listening! Joyeux anniversaire, ISOLDE!