Recent achievements in the search for superheavy elements H.W ...

Recent achievements in the search for superheavy elements H.W ...

Trends in heavy ion sciences 24 May, 2008 Why experimenters like to come to Dubna: Scientific success is always a good reason to organize a big party! Trends in heavy ion sciences 24 May, 2008 Laboratory for Radiochemistry and Environmental Chemistry How chemists have reached the island of spherical superheavy elements Heinz W. Gggeler Paul Scherrer Institut and Bern University, Switzerland Chemistry of volatile 7p-elements = chemistry of spherical SHE Recent studies with IVO: In-Situ volatilisation and Online detection (developed for first chemical study of hassium but recently applied for element 112 and 114) Are relativistic effects influencing the chemical property of element 114? Trends in heavy ion sciences 24 May, 2008 island of Superheavy Elements Number of protons 114 peak of U peak of Pb 82 strait of radioactivity sea of instability 50 strait of instability peak of Sn 20 sea of instability peak of Ca 20 82 126 Number of neutrons G.N. Flerov, A.S. Ilyinov (1982) 184 Shell stabilisation spherical deformed Courtesy: S. Hofmann

Trends in heavy ion research, 24 May 2008 Periodic Table Table of the Elements Periodic of the 1 18 1 2 H 2 13 14 15 16 17 He 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 11 12 13 14 15

16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar 19 20 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 45 47 48 49 50 51 52 53 54 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn

Sb Te I Xe 72 73 74 75 76 78 79 80 81 82 83 84 85 86 La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 89 104 105 106

Rf Db 107 115 115 116 116 116 69 70 Rb Sr 21 55 56 57 Cs Ba 87 88 Fr Ra Ac Lanthanides Actinides 58 59 Sg Bh 60 61 44 77 46 108 Hs 62 114 112 109 110

111 Mt Ds Ds Rg Rg 63 64 65 113 113 114 66 67 68 118 118 -- 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 90 91 92 93 96 98 99 100 101 103 Th Pa U

Np Pu Am Cm Bk Cf Es Fm Md No Lr 94 95 97 102 Mendelejevs first Periodic Table from 1871 Basis for the discovery of several new elements! Positioning of new elements into the Periodic table 1 18 1 2 H 2 3 4 Li Be 11 12 1993 2007 -- 1997 2001 2000 2007 2002 13 14 15 16 17 He 5 6

7 8 9 10 B C N O F Ne 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar 19 20 22 23

24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 45 47 48 49

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag 55 56 57-71 72 73 74 75 76 78 Cs Ba La Hf Ta W Re Os Ir Pt 87 88 89-103 104 105 106 107 Fr Ra Ac Rf Db Sg 21 44

77 58 59 Lanthanides La Ce Pr Actinides 60 51 52 53 54 Cd In Sn Sb Te I Xe 79 80 82 83 84 85 86 Au Hg Tl Pb Bi Po At Rn 112 114 115 116 61 81 --

108 107 109 110 62 111 63 64 -- 112 Ds Rg Mt Sg Bh Hs 57 50 108 Bh Hs 106 46 -- 65 114 113 -- 66 67 68 118 -- 69 70 71 Nd Pm Sm Eu Gd Tb Dy Ho Er

Tm Yb Lu 96 98 99 100 101 103 Cf Es Fm Md No Lr 89 90 91 92 93 94 95 97 Ac Th Pa U Np Pu Am Cm Bk 102 Reactions used and number of atoms found in the first ever chemical studies in the last decade Bohrium (Z=107); Main experiment at PSI 249Bk(22Ne;4n)267Bh (T 1/2 = 17 s); 6 atoms (R. Eichler et al., Nature, 407, 64 (2000)) Hassium (Z=108); Main experiment at GSI 248Cm(26Mg;5n)269Hs(T 1/2 = 15 s); 7 atoms (C.E. Dllmann et al., Nature, 418, 860 (2002)) Element 112; Main experiment at FLNR/JINR 242Pu(48Ca,3n)287114 (T 283 1/2 = 0.5 s) 112 (T1/2 = 4 s); 2 atoms (R. Eichler, Nature, 447, 72,2007); meanwhile 5 atoms in total (R. Eichler et al., Angew. Chem. Int. Ed., 47,1(2008)) Element 114: Main experiment at FLNR/JINR; ongoing. Currently evidence for 3 - 5 atoms Trends in heavy ion research, 24 May 2008 Gas flow Yield [%] Temperature [C]

Isothermal Chromatography: Sg,Bh T50% tRet. = T1/2 low Temperature [C] high Column length [cm] Ta Gas flow Yield [%] Temperature [C] Thermochromatography: Hs, Z=112; Z=114 Column length [cm] high Temperature [C] low 1 Elements with Z 112: filled 6d10 shell: 7p-element behaviour (volatile noble metals) 18 1 2 H 2 13 14 15 16 17 He 3 4 5 6 7 8 9 10 Li Be B

C N O F Ne 11 12 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar 19 20 22 23 24 25 26

27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 45 47 48 49 50 51 52

53 54 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 72 73 74 75 76 78 79 80 81 82 83 84 85 86 La Hf Ta W Re Os Ir Pt Au Hg

Tl Pb Bi Po At Rn 89 104 105 106 Rf Db 107 115 115 116 116 116 69 70 Rb Sr 21 55 56 57 Cs Ba 87 88 Fr Ra Ac Lanthanides Actinides 58 59 Sg Bh 60 61

44 77 46 108 Hs 62 114 112 109 110 111 Mt Ds Ds Rg Rg 63 64 65 113 113 114 66 67 68 118 118 -- 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 90 91 92 93

96 98 99 100 101 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 94 95 97 102 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 50 500 45 450 Hg Hads = -87 kJ/mol 219 Rn Hads = -27 kJ/mol 400 35 350 30 300

25 250 20 200 15 150 10 100 5 50 0 0 1 3 5 7 9 11 13 15 17 19 lenght [cm] 21 23 25 27 29 31 temperature [K] yield [%] 40 192 Adsorption of single atoms of mercury and radon on a quartz surface 50 500 Hg Hads = -24.5 kJ/mol 219 Rn Hads = -20.5 kJ/mol 192

400 350 40 yield [%] 450 300 30 250 200 20 150 100 10 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 lenght [cm] temperature [K] 60 Correlation between adsorption properties of single atoms on gold and their macroscopic sublimation enthalpy Trends in heavy ion science, 24 May 2008 Element 112 similar to Hg? 1 18 1 2 H 2 13 14 15 16 17 He 3 4 5 6

7 8 9 10 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar

19 20 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43

45 47 48 49 50 51 52 53 54 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 72 73 74 75 76 78 79 80 81 82 83 84 85 86 La

Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 89 104 105 106 Rf Db 107 115 115 116 116 116 69 70 Rb Sr 21 55 56 57 Cs Ba 87 88 Fr

Ra Ac Lanthanides Actinides 58 59 Sg Bh 60 61 44 77 46 108 Hs 62 112 109 110 111 Mt Ds Ds Rg Rg 63 64 65 114 113 113 114 66 67 68 118 118 -- 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy

Ho Er Tm Yb Lu 90 91 92 93 96 98 99 100 101 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 94 95 97 102 Texas A&M, Nov. 2007 The element 112 experiment (IVO [In-situ Volatilisation and On-line detection] Technique) Beam (48Ca; 233-239 MeV) Window/ Target (242Pu: 1.4 mg/cm2) Recoil chamber Beam stop Teflon capillary SiO2-Filter Ta metal 850C

Quartz inlay Cryo On-line Detector (4 COLD) (32 pairs PIN diodes, one side gold covered) 11 Loop Rn 2 Temperature gradient: 35C to 184 C Hg Quartz column T Carrier gas He/Ar (70/30) l Studies on element 112 Pu(48Ca;3n)287114 (0.5 s) 4s 283112 Reasons a) High cross section of 5 pb ( 3-times higher than via direct production with 238U as a target) b) Residence time in collection chamber and transport 283 112 capillary 2 s 242 4s 9.54 MeV Rf Ds261 279 4s 0.2 s 8.5 MeV Trends in heavy ion science, 24 May 2008 Excitation functions C r o s s s e c t io n s / 3 M e V ( r e la t iv e u n it s ) xn-channel cross sections from 242,244Pu+48Ca reactions Courtesy: Yu. Oganessian. Heaviest Nuclei from 48 50 10 3n

5 2n 3n 4n 5n 4n 1 2n 0 .5 5n 0 .1 25 30 35 55 50 40 45 E x c it a t io n e n e r g y ( M e V ) Ca-induced Reactions TAN-07, Davos, Sept. 23-27, 2007 Trends in heavy ion science, 24 May 2008 Laboratory for Radiochemistry and Environmental Chemistry Result from the 48Ca + 242Pu experiment Observed in Chemistry: 11.05.2006 2:40 (moscow time) 287 25.05.2006 8:37 (moscow time) 114 114 287 First independent confirmation of 283112 formation and 112 112 decay properties! (R. Eichler et al., Nature, 447, 72 (2007)) 283 283 9.48 MeV 9.37 MeV 279 Ds 279 Ds : 0.592 s SF : 0.536 s SF

108+123 MeV 127+105 MeV Three week bombardment with 3.1x1018 48Ca ions at 236 3 MeV Result from additional 48Ca + 242Pu experiments in 2007 The chemistry experiment is not sensitive to the 4n channel (too short-lived nuclides) 114 287 287 112 112 283 283 Ds 279 Ds : 0.072 s SF : 0.773 s SF 112 + n.d MeV 85+12 MeV 287 283 9.35 MeV 9.52 MeV 279 114 114 112 9.52 MeV 279 Ds : 0.088 s SF 94+51 MeV Bombardment 21.3.- 17.4. 2007 with 3.1x1018 48Ca ions at 237 3 MeV The chemistry of element 112 Element 112 is similar to Hg, but slightly more volatile Deduced adsorption enthalpy:

-52+20-4 kJ/mol (black solid line) The chemistry of element 112 -52+20-4 kJ/mol Hsubl=39+23-10 kJ/mol (68% c.i.) Trends in heavy ion science, 24 May 2008 Trend of sublimation enthalpy within group 12 Trends in heavy ion science, 24 May 2008 Whats next? Search for relativistic effects in the chemistry of element 114 (group 14 with [Rn]7s26d107p2) Relativistic effect: influence of increasing Coulomb attraction between atomic electrons and nucleus Trends in heavy ion science, 24 May 2008 Group 14: 6d107s27p2 Prediction by Pitzer (1975) Is element 114 a noble gas due to a strong spin-orbit splitting of the 7p orbitals? from: V. Pershina et al., J. Chem. Phys., 127, 134310 (2007) Studies on element 114 Reaction: 242Pu(48Ca;3n)287114 (T1/2 =0.5s) (FLNR; spring 2007) 114 287 1 atom on Au at 80 C 10.0 MeV 3.1x1018 48Ca ions at 237 3 MeV 283 112 10.9 s 9.54 MeV Rf Ds261 279 4s 0.24s 8.5 MeV unpublished Trends in heavy ion science, 24 May 2008 Studies on element 114 Reaction: 244Pu(48Ca;4n)288114 (T1/2 =0.8s) 2 atoms on Au at 10 C & -84 C Beam dose 4x1018 Energy within targets: 243 231 MeV

(~ 1.4 mg/cm2) unpublished 288 114 9.95 MeV 284261 Rf 112 4s 0.11 s 8.5 MeV 288 114 9.81 MeV 112 284 0.11 s Trends in heavy ion science, 24 May 2008 Current experiment lasting until 8 June 2008 at FLNR: 48 Ca + 244Pu to produce 0.8 s 288114 (4n-channel) 2.7 s 289114 (3n-channel) Chemistry behind the Dubna gasfilled separator Pro & Contra Pro: - Extremely clean - spectra (no background) - no sf-contamination by sputtered target Contra: - Lower efficiency - Smaller energy range in the thin target Studies on element 114 Reaction: 244Pu(48Ca;3n)289114 (T1/2 =2.7s) (FLNR; ongoing 2008) 1 atom on Au at 97 C 285 4x1018 48Ca ions at E* = 38 42 MeV 289 114 Not detected 112

9.12 MeV 281261 Rf Ds 4s 3.3s 8.5 MeV SF 106+50 unpublished Trends in heavy ion science, 24 May 2008 50 gold ice Rel. yield / detector, % 8 287 114 6 Au Hads =-35 kJ/mol 4 2 0 10 gold e r P 8 il m -50 y r a in -100 -150 -200 50 ice 0 288 6 Au ads

H 4 Pu-244 0 114 -50 =-35 kJ/mol 2 -100 -150 0 -200 2 4 6 8 10 Decay during transport? 12 14 16 18 20 Detector # unpublished 22 24 26 28 30 32 Temperature, C Pu-24210 250 Po Pb experimantal data least square fit: 95% c.i.

Tl Hg E114 Bi -Hads (Au), kJ/mol 200 150 100 At Xe 50 r P Rn m i l e y r a in -Hads(Au) = (1.080.05)*Hsubl+(10.36.4), kJ/mol Kr 0 0 50 100 150 Hsubl, kJ/mol 200 250 Result from the chemistry experiment with element 114 Element 114 exhibits a very weak adsorption on Au, pointing to van der Waals interaction (similar to a noble gas). Conclusion

Chemical research on heaviest elements has been much boosted by the recent discoveries of many new nuclides up to Z=118 at FLNR Chemical studies at the few atom level have been sucessfully conducted up to Z = 112 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. Trends in heavy ion science, 24 May 2008 Many thanks To Yuri Oganessian for his constant support and very active engagement in the experiments To Sergei Dmitriev and his team for the Dubna chemists To Georgi Gulbekian and his team for the excellent 48Ca beams To Robert Eichler and his team from the PSI/Univ. Bern collaboration Trends in heavy ion science, 24 May 2008 Raw data from few-hour measurement with pre-separation (GNS) (left) and without (right) 219 Rn 215 Po 211 At Po 214 212 Po

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