1. Radioactive beam spectroscopy of 212 Po and 213 At with the EXOGAM array Nick Thompson University of Surrey

2. Aim The production of high spin states in 212 Po and 213 At Analysis of resulting spectra to look for: ● New transitions ● population of spin states ● contamination

3. 8He radioactive beam Produced by SPIRAL facility at GANIL through fragmentation of 13C primary beam on thick carbon target. [M Lewitowicz, Nucl. Phys. a734, 645c (2004)] 8He particles (T 1/2 = 119 ms) accelerated to 28 MeV Av. intensity 2x10 5 ions/s ~2x that of previous experiment. [Zs Podolyak et al., Nucl. Inst. and Meth. in Phys. Res A511, 354 (2003)] Targets: 208 Pb (30 and 50 mg/cm 2 ) in beam for ~4.5 and 0.5 days respectively 209 Bi (50 mg/cm 2 ) for ~1 day

4. Reactions ● Excited states of 212 Po and 213 At populated with ( 8 He, 4n) reactions ● Both with cross section ~500mb ● 8 He + 208 Pb → 216 Po * → 212 Po * + 4n ● 8 He + 209 Bi → 217 At * → 213 At * + 4n also important from beam: ● 8 He → 8 Li * + β -

5. Detection system Four EXOGAM Compton-suppressed clover detectors in the “gamma-cube configuration” Fig.2. 1 Fig.4. 1 Fig.3. with the average distance from target to detector at 68mm the full-energy-peak efficiency at 662 keV was 13.5% data acquisition master trigger set to singles Diagrams: http://www.ganil.fr/exogam/

6. Analysis Main fusion-evaporation products are 212 Po and 213 At. 209 Pb and 210 Bi also created through single neutron pick-up between beam and target. All these nuclei have been studied previously: 212 Po [A R Poletti et al. Nucl. Phys. A473, 595 (1987)] 213 At [G J Lane et al.,AIP Conference Proceedings, 656, 386c (2003)] 209 Pb and 210 Bi [R B Firestone et al.,Table of Isotopes, Eighth edition, Wiley, New York, 1996]

7. Analysis spectra from coincidence data 727 keV 2 + → 0 + gate 212 Po decay scheme based in work by A R Poletti et al. Nucl. Phys. A473, 595 (1987) and T R McGoram, M.Sc Thesis, University of Aukland, New Zealand (1997), and to be published 18 + state at 2921.0 keV α-decays to 208 Pb ground state

8. Analysis Evidence is found for a previously unreported 69 keV transition (13 - ) → (12 + ) in gated γ-γ spectra with conditions that at least two Clovers fire in the same event (within 2 μs) 182.8(4) keV (14 + ) → (12 + ) transition seen, completing even-parity yrast states to spin 14 + this has previously been observed in coincidence with α particles following the 9 Be reaction [T R McGoram, M.Sc Thesis, University of Aukland, New Zealand (1997), and to be published] 69 Gate on 577 Gate on 868

9. Relative intensity comparison of our 8 He beam work and 9 Be induced reaction performed by A R Poletti et al. Nucl. Phys. A473, 595 (1987)

10. Conclusions Possible new transition identified at 69 keV Sighting of 182.8 keV transition (previously seen but not available in general literature Apparent increase in population of higher spin states to 12 + 213 At preliminarily observed to spin (39/2 - ) - work in progress Continuing search for peak in spectra which might be attributable to a state higher than 18 +

11. A.B. Garnsworthy 1, Zs. Podolyák 1, P.M. Walker 1, S.J. Williams 1, G.D. Dracoulis 2, G. de France 4, G.J.Lane 2, K. Andgren 1,5, A.M. Bruce 6, A.P. Byrne 2,3, W.N. Catford 1, B. Cederwall 5, G.A. Jones 1, B. McGuirk 7, S. Mandal 8 E.S. Paul 7, V. Pucknell 9, N. Redon 10, B. Rosse 10, R.J. Senior 2 and G. Sletten 11 Many thanks to my collaborators – 1. Department of Physics, University of Surrey, Guildford GU2 7XH, UK – 2. Dept. of Nuclear Physics, Australian National University, Canberra, Australia – 3. Dept. of Nuclear Physics, The Faculties, Australian National University, Canberra, Australia – 4. GANIL, BP 5027, Caen Cedex F-14021, France – 5. Department of Physics, Royal Institute of Technology, S-106 91, Stockholm, Sweden – 6. School of Engineering, University of Brighton, Brighton BN2 4GJ, UK – 7. Department of Physics, University of Liverpool, Liverpool, L69 3BX, UK – 8. GSI, Planckstrasse 1, Darmstadt D-64291, Germany – 9. CLRC Daresbury Laboratory, Warrington, WA4 4AD, UK – 10. Institut de Physique Nucleaire de Lyon, Lyon, France – 11. Niels-Bohr-Institute, DK-2100 Copenhagen, Denmark Also thanks to my sponsors BNFL