CERN, August 2008

HAPPY LANDING ON THE ISLAND OF SUPERHEAVY ELEMENTS Heinz W. Gäggeler Paul Scherrer Institut and Bern University, Switzerland Laboratory for Radiochemistry and Environmental Chemistry

sea of instability island of Superheavy Elements Number of neutrons Number of protons peak of Sn peak of Ca peak of Pb peak of U strait of radioactivity strait of insta- bility G.N. Flerov, A.S. Ilyinov (1982)

CERN, August 2008 Shell stabilisation Courtesy: S. Hofmann deformed spherical

CERN, August 2008 Courtesy: M. Schädel The Dubna claims using 48 Ca induced fusion reactions with actinides targets

Periodic Table of the Elements Ds H Li Na K Rb Cs FrRaAc Ba Sr Ca Mg Be Sc Y La Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os CoNiCuZnGaGeAs RhPdAgCdInSnSb IrPtAuHgTlPbBi RfDb Sg BCNOF AlSiPSCl SeBr TeI PoAt CePrNdPmSmEuGdTbDyHoErTmYbLu ThPaUNpPuAmCmBkCfEsFmMdNoLr Lanthanides Actinides Bh 107 Hs Mt Rg He Ne Ar Kr Xe Rn

H Li Na K Rb Cs FrRaAc Ba Sr Ca Mg Be Sc Y La Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os CoNiCuZnGaGeAs RhPdAgCdInSnSb IrPtAuHgTlPbBi RfDb BCNOF AlSiPSCl SeBr TeI PoAt Lanthanides Actinides He Ne Ar Kr Xe Rn CePrNdPmSmEuGdTbDyHoErTmYbLu ThPaUNpPuAmCmBkCfEsFmMdNoLr La Ac Positioning of new elements into the Periodic Table Sg 106 Bh 107 Hs 108 Mt Ds Rg Sg Bh 107 Hs ≥

CERN, August 2008 Reactions used and number of atoms found in the „first ever chemical studies“ during the last decade Bohrium (Z=107); Main experiment at PSI 249 Bk( 22 Ne;4n) 267 Bh (T 1/2 = 17 s); 6 atoms (R. Eichler et al., Nature, 407, 64 (2000)) Hassium (Z=108); Main experiment at GSI 248 Cm( 26 Mg;5n) 269 Hs (T 1/2 = 15 s); 7 atoms (C.E. Düllmann et al., Nature, 418, 860 (2002)) Element 112; Main experiment at FLNR/JINR 242 Pu( 48 Ca,3n) (T 1/2 = 0.5 s)  (T 1/2 = 4 s); 2 atoms (R. Eichler, Nature, 447, 72,2007); meanwhile 5 atoms in total (R. Eichler et al., Angew. Chem. Int. Ed., 47, 3262 (2008)) Element 114: Main experiment at FLNR/JINR; ongoing. Currently evidence for 4 atoms

Isothermal Chromatography: Sg,Bh Temperature [°C] Column length [cm] Temperature [°C] Yield [%] 50% T t Ret. = T 1/2 Gas flow highlow Thermochromatography: Hs, Z=112; Z=114 Temperature [°C] Column length [cm] Temperature [°C] Yield [%] T a high Gas flow low Example: Chemical study of bohrium Example: Chemical study of elements 112 and 114

CsCl aerosols reaction oven 118MeV 22 Ne 22 Ne 249 BkFUSION 271 Bh* 267 Bh 249 Bk HCl O2O2 He chromatography column Ar to detection system ROMA carbon aerosols reaction products On-Line Gas chromatography Apparatus Continuous on-line chemistry Example: bohrium

How to detect single atoms? Textbook example: Discovery of element 112 SHIP :37 SHIP : MeV 280  s 111 MeV 110  s 2222 269 Hs 9.23 MeV 19.7 s 3333 265 Sg 4.60 MeV (escape) 7.4 s 4444 261 Rf 8.52 MeV 4.7 s 5555 257 No 8.34 MeV 15.0 s 6666 70 Zn Pb → n

First chemical characterization of bohrium (Z=107) bohrium (Z=107) T isothermal (°C) Relative yield (%) TcO 3 Cl 108 (T 1/2 = 5.2 s) H a = -51 kJ/mol  (T 1/2 = 16 s) ReO Cl  H a = -62 kJ/mol BhO 3 Cl 267 (T 1/2 = 17 s) = kJ/mol H a  0 atoms 2 atoms 4 atoms R. Eichler et al., Nature, 407, 63 (2000)

Elements with Z ≥ 112: filled 6d 10 shell: 7p-element behaviour (volatile noble metals) Ds H Li Na K Rb Cs FrRaAc Ba Sr Ca Mg Be Sc Y La Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os CoNiCuZnGaGeAs RhPdAgCdInSnSb IrPtAuHgTlPbBi RfDb Sg BCNOF AlSiPSCl SeBr TeI PoAt CePrNdPmSmEuGdTbDyHoErTmYbLu ThPaUNpPuAmCmBkCfEsFmMdNoLr Lanthanides Actinides Bh 107 Hs Mt Rg He Ne Ar Kr Xe Rn

How to experimentally determine a metallic character of a volatile element at a single atom level? → Determine interaction energy (adsorption enthalpy) with noble metals (e.g. Au) → If metallic: strong interaction (adsorption enthalpy) if non-metallic (noble gas like): weak interaction

Adsorption of single atoms of mercury and radon on a gold surface

Adsorption of single atoms of mercury and radon on a quartz surface

CERN, August 2008 Correlation between adsorption properties of single atoms on gold and their macroscopic sublimation enthalpy

Texas A&M, Nov Ds H Li Na K Rb Cs FrRaAc Ba Sr Ca Mg Be Sc Y La Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os CoNiCuZnGaGeAs RhPdAgCdInSnSb IrPtAuHgTlPbBi RfDb Sg BCNOF AlSiPSCl SeBr TeI PoAt CePrNdPmSmEuGdTbDyHoErTmYbLu ThPaUNpPuAmCmBkCfEsFmMdNoLr Lanthanides Actinides Bh 107 Hs Mt Rg He Ne Ar Kr Xe Rn Element 112 similar to Hg?

Window/ Target ( 242 Pu:  1.4 mg/cm 2 ) Beam ( 48 Ca; MeV) Beam stop SiO 2 -Filter Ta metal 850°C Quartz column Cryo On-line Detector (4  COLD) Carrier gas He/Ar (70/30) Teflon capillary (32 pairs PIN diodes, one side gold covered) Hg Loop Temperature gradient: 35°C to – 184 °C T l Rn The element 112 experiment (IVO [In-situ Volatilisation and On-line detection] Technique) 112 Recoil chamber Quartz inlay

CERN, August 2008 Studies on element Pu( 48 Ca;3n) (0.5 s) → 4s Pu( 48 Ca;3n) (0.5 s) → 4s Reasons a) High cross section of  5 pb ( 3-times higher than via direct production with 238 U as a target) Reasons a) High cross section of  5 pb ( 3-times higher than via direct production with 238 U as a target) b) Residence time in collection chamber and transport capillary  2 s b) Residence time in collection chamber and transport capillary  2 s  9.54 MeV 4 s Rf s  8.5 MeV Ds s

CERN, August 2008 xn-channel cross sections from 242,244 Pu+ 48 Ca reactions Excitation functions Courtesy: Yu. Oganessian. “Heaviest Nuclei from 48 Ca-induced Reactions” TAN-07, Davos, Sept , 2007

MeV Ds  : s SF MeV Observed in Chemistry: :40 (moscow time) MeV Ds  : s SF MeV :37 (moscow time) Result from the 48 Ca Pu experiment Laboratory for Radiochemistry and Environmental Chemistry Three week bombardment with 3.1 x Ca ions at 236 ± 3 MeV First independent confirmation of formation and decay properties! (R. Eichler et al., Nature, 447, 72 (2007))

MeV Ds  : s SF MeV Result from additional 48 Ca Pu experiments in 2007: 3 additional atoms from the 3n channel Bombardment with 3.1x Ca ions at 237± 3 MeV MeV Ds  : s SF n.d MeV MeV Ds  : s SF MeV The chemistry experiment is not sensitive to the 4n channel (too short-lived isotope)

The chemistry of element 112 Element 112 is similar to Hg, but slightly more volatile Deduced adsorption enthalpy: kJ/mol (black solid line)

CERN, August 2008 The chemistry of element 112  H subl = kJ/mol (68% c.i.) kJ/mol

CERN, August 2008 Trend of sublimation enthalpy within group 12

CERN, August 2008 What‘s next? Search for relativistic effects in the chemistry of element 114 (group 14 with [Rn]7s 2 6d 10 7p 2 ) Relativistic effect: influence of increasing Coulomb attraction between atomic electrons and nucleus

CERN, August 2008 Primary relativistic effect: s p 1/2 p 3/2 d 3/2 d 5/2 f 5/2 f 7/2 m= 1/2 m=-1/2 m= 1/2 m=-1/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= 5/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= -5/2 m= 7/2 m= 5/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= -5/2 m= -7/2 White 1931

CERN, August 2008 Secondary relativistic effect: s p 1/2 p 3/2 d 3/2 d 5/2 f 5/2 f 7/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= 5/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= -5/2 m= 7/2 m= 5/2 m= 3/2 m= 1/2 m= -1/2 m= -3/2 m= -5/2 m= -7/2 White 1931 Spin-Orbit splitting splitting m= 1/2 m=-1/2 m= 1/2 m=-1/2

from: V. Pershina et al., J. Chem. Phys., 127, (2007) Group 14: 6d 10 7s 2 7p 2 Prediction by Pitzer (1975) Is element 114 a noble gas due to a strong spin-orbit splitting of the 7p orbitals?

CERN, August 2008 Studies on element 114 Reaction: 242 Pu( 48 Ca;3n) (T 1/2 =0.5s) (FLNR; spring 2007) Reaction: 242 Pu( 48 Ca;3n) (T 1/2 =0.5s) (FLNR; spring 2007) Rf s  8.5 MeV Ds s s  9.54 MeV  10.0 MeV 1 atom on Au at – 80 °C 3.1 x Ca ions at 237± 3 MeV unpublished

CERN, August 2008 Studies on element 114 Reaction: 244 Pu( 48 Ca;4n) (T 1/2 =0.8s) Reaction: 244 Pu( 48 Ca;4n) (T 1/2 =0.8s) Rf s  8.5 MeV 2 atoms on Au at –10 °C & -84 °C Beam dose 4x10 18 Energy within targets: 243 – 231 MeV (~ 1.4 mg/cm 2 )  9.95 MeV  9.81 MeV s unpublished

Experiment April/May at FLNR: 48 Ca Pu to produce 0.8 s (4n-channel) 2.7 s (3n-channel) Chemistry behind the Dubna gas- filled separator

Pro & Contra Pro: - Extremely clean  - spectra (no background) - no sf-contamination by sputtered target Contra: - Lower efficiency (thin target & 35% sep.yield) - Smaller energy range in the thin target

CERN, August 2008 Studies on element 114 Reaction: 244 Pu( 48 Ca;3n) (T 1/2 =2.7s) (FLNR; 2008) Reaction: 244 Pu( 48 Ca;3n) (T 1/2 =2.7s) (FLNR; 2008) Rf s  8.5 MeV 281 Ds 3.3s  9.12 MeV Not detected 1 atom on Au at – 97 °C 4 x Ca ions at E* = 38 – 42 MeV SF unpublished

Decay during transport? Preliminary unpublished

E114 Preliminary

Result from the chemistry experiment with element 114 → Element 114 exhibits a very weak adsorption on Au - pointing to a physisorptive van der Waals interaction (similar to a noble gas). Preliminary!

CERN, August 2008 Conclusion Chemical studies at the few atom level have been sucessfully conducted up to Z = 114 Chemical studies at the few atom level have been sucessfully conducted up to Z = 114 Elements Bh, Hs & 112 (as well as Rf, Db, Sg) behave in gas phase studies as expected from extrapolations within the groups of the periodic table Elements Bh, Hs & 112 (as well as Rf, Db, Sg) behave in gas phase studies as expected from extrapolations within the groups of the periodic table Ongoing studies point to an element 114 behaviour unlike that of eka-Pb, but rather similar to a noble gas. Ongoing studies point to an element 114 behaviour unlike that of eka-Pb, but rather similar to a noble gas.

CERN, August 2008 Acknowledgement Yuri Oganessian, Sergei Dmitriev and Georgi Gulbekian Yuri Oganessian, Sergei Dmitriev and Georgi Gulbekian Robert Eichler and his team from the PSI/Univ. Bern collaboration Robert Eichler and his team from the PSI/Univ. Bern collaboration