Status Report on Decay Spectroscopy and In-Source Laser Spectroscopy on Heavy Nuclei at ISOLDE Piet Van Duppen ISOLDE CERN, Switzerland IKS-K.U.Leuven, Belgium K.U. Leuven University of Western Scotland, U.K. - K.U.Leuven, Belgium - SCK-CEN-Mol, Belgium - U.Gent, Belgium - Commenius University, Slovakia - Institute of Physics, Slovak Academy of Sciences - ILL-Grenoble, France - ISOLDE-CERN, Switzerland - U.Mainz, Germany - TRIUMF, Canada - JAEA, Tokai, Japan - LPC-Caen, France - PNPI Gatchina, Russia Spokesperson(s): Andrei Andreyev, Yuri Kudryavtsev, Anatoly Barzakh, Valentine Fedosseev - IS456: Study of polonium isotopes ground state properties by simultaneous atomic- and nuclear-spectroscopy - IS466: Identification and systematical studies of the electron-capture delayed fission (ECDF) in the lead region - Part I: ECDF of 178,180Tl and 200,202Fr isotopes - IS511: Shape coexistence in the lightest Tl isotopes studied by laser spectroscopy - I86: Development of astatine ion beams with RILIS

2 178 Tl 150 ms  178,180,182 Tl Z=82 200,202,204 Fr 192,194,196 At N/Z~1.25 Outline Decay spectroscopy Beta-delayed fission (Tl, Fr, At) Beta-delayed gamma In-Source Laser Spectroscopy (Pb, Po) At laser ionization scheme development polonium lead astatine Physics Study of fission fission barriers,  DF process – ending of the r-process nucleosynthesis Shape Coexistence in the Z=82 region

- particle induced x - e.m. –induced E*~11 MeV 187 Ir 196 Au Z=82 Actinide nuclei N/Z~1.56: predominantly asymmetric; spontaneous fission, fission isomers Pre-actinides and light At-Th N/Z~ : predominantly symmetric (e.g. FRS(GSI)) K.-H. Schmidt et al. Z= Hg N/Z=1.25 Region of our interest:  DF of nuclei with A~ , N/Z~ IS466: Beta-delayed fission of neutron-deficient isotopes

deformation 180 Tl(Z=81,N=99) Q EC MeV B f ~ 10 MeV 180 Hg (Z=80, N=100) low-energy fission! (E*~3-12 MeV) 10 cases known before this work (neutron-deficient Uranium region)     + /EC  DF NN N  DF  DF branch P  DF = N  DF N  If P  DF is measured, one can deduce fission barrier B f Need to know Q EC,thus masses should be known Beta-strength function S  :TAS experiments Q EC  f (B f )  tot (E) P  DF ~  (Q EC -E) 2  S  dE  (Q EC -E) 2  S  (E)dE 0 0 Q EC IS466: Beta-delayed fission studies

P  DF ( 180 Tl) = 3.6(7) % (this work, A. Andreyev,- PRL 105 (2010) ) P  DF ( 180 Tl) = % (Lazarev,-, EPL 4 (1987) 893: ) IS466: Beta-delayed fission studies: 180 Tl

180 Hg (Z=80, N=100, N/Z=1.25) does not fission in two semi-magic 90 Zr(Z=40,N=50) 100 Sn (N/Z=1) Atomic Number Z Neutron Number N N/Z= Ru 80 Kr 90 Zr 78 Ni (N/Z=1.78) Ground-state shell corrections (P. Moller) PES calc. according to a 5 dim. fission model (P. Moller,- Nature 409, 785 (2001) Several other theory groups are currently working on this intriguing observation (W. Nazarewicz, P.H.Heenen, K.H. Schmidt,..) MeV

E ff2 (MeV) Counts E ff1 (MeV) E ff1 -E ff2 coincidences (42 events)  DF of 202 Fr ~2 singles ff/h Singles ff in one detector 62 events 202 Rn: Symmetric mass split in nuclei around 100 Mo- 100 Ru E ff1 -E ff2 coincidences ~330 events Counts E ff2 (MeV) E ff1 (MeV)  DF of 180 Tl, ~20 singles ff/h 180 Hg: Asymmetric mass split in nuclei around 80 Kr and 100 Ru Mass distribution of 202 Rn via  DF of 202 Fr May ISOLDE Why nuclei around 100 Ru, 100 Mo (Z=42-44, N~58)? Calculated gs deformation:  2 ~ gs shell corrections: MeV (cf: MeV for 132 Sn) Large shell corrections at strongly deformed scission shapes relevant to fission?

PRELIMINARY! Even at E*=66 MeV: asymmetric mass split with A 1 ~100, A 2 ~80 ISOLDE - CERN: In-source laser spectroscopy thallium isotopes (IS511 July 2011) 200,202,204 Fr (May 2011, July 2011) 196,194 At (I86: May 2011) Beta-strength function using TAS Alpha-decay studies (under analysis) JAEA,Tokai,Japan 36 Ar+ 144 Sm-> 180 Hg* E*=34-66 MeV GSI, Darmstadt, Germany: low-energy e.m. Induced fission: 180 Tl Future studies V. Liberati PhD Thesis, UWS – Paisley L. Ghys, PhD Thesis, K.U.Leuven fissions/h 180 Tl20P  DF / mass distr. 178 Tl0.35P  DF 202 Fr2.0P  DF / mass distr. 196 At3-4P  DF / mass distr.

Beta-delayed gamma decay of 180,182 Tl to 180,182 Hg No evidence for an beta-decaying isomer in 180 Tl: I  = (4 -,5 - ) Identification of the state in 180 Hg Conversion coefficient transition: 3.5 (4) for 180 Hg – 4.1(7) for 182 Hg (confirmed from in-beam electron spectroscopy JYFL: R. Page et al.) electron spectrum

Beta-delayed gamma decay of 180,182 Tl to 180,182 Hg 182 Hg 2 + -> > >0 + Energy Counts Input for Hg Coulex data analysis (IS452) J. Elseviers, PhD Thesis, K.U.Leuven and to be published in PRC 2011

T.E. Cocolios et al., PRL 106 (2011) M. Seliverstof et al., EPJ A41(2009) 315 H. De Witte et al., PRL 98 (2007) IS456: In-source laser spectroscopy: lead, polonium, thallium, astatine

Comparison with beyond-mean-field calculations T.E. Cocolios et al., PRL 106 (2011) Calculations: P.H. Heenen, M. Bender et al.

Polonium isotopes: deduced moments (M. Seliverstof,- to be published) confronted with results from Po Coulex data (IS479) and life times (T. Grahn,- PRL97 (2006) ) comparison with theory: beyond mean field calculations and IBM type calculations Thallium isotopes (IS511): In-source laser spectroscopy: charge radii, spins, isomers, moments ( 180 Tl) Mercury isotopes: beyond the isomer/ground state staggering (proposal in preparation) Astatine (see further)

I86: On-line resonant ionization of astatine (2010) S. Rothe, PhD Thesis, U.Mainz Only two excitation steps known (R. McLaughlin, J. Opt. Soc. Am. 54, 965 (1964)). Ionization Potential was not known Collaboration with TRIUMF (J. Lassen)

First measurement of the IP of Astatine IP(At) = cm -1 (9.31 eV) I86: On-line resonant ionization of astatine (2010)

I86: On-line resonant ionization of astatine (2011) 205 At Laser scans for 196,218 At and production rates down to 192,194 At

I86: On-line resonant ionization of astatine (2011) Outlook Scanning 2 nd and 3 th step optimizing scheme and searching for auto ionizing states Investigate Hyperfine Structure preparation for in-source laser spectroscopy and isomer separation Use the new astatine beams: beta-delayed fission, beta- and alpha decay, laser spectroscopy, mass measurements,.., Thanks to the spokespersons and to S. Rothe, T.E. Cocolios and V. Liberati