Chemistry of Spherical Superheavy Elements – The Road to Success

sea of instability island of spherical SHE Number of neutrons Number of protons peak of Sn peak of Ca peak of Pb peak of Th,U strait of radioactivity S. Soverna January 2004

287   5 s sf  3 min Hs 277 sf  10  min 285   10 min   1 min Ds 289   20 s   45 s 112   2.6 s sf  7.6 s Ds 292   53 ms 116 Rf 253 sf 48  s Rf 254 sf 23  s Rf 256 sf,  6.2  s Rf 257 ,ec 4.7s ,ec Rf 258 sf 13 ms Rf 259 ,sf 3.1 s Rf 260 sf 21 ms Rf 261  78 s Rf 262 sf 47ms 1.4s Rf 255 ,sf 0.8s ,sf 1.4s2.1s sf Db 257 ,sf 1.3 s Db 258 ,ec 4.4 s Db 260 ,ec/sf? 1.5 s Db 261 ,sf 1.8 s Db 262 ,ec/sf? 34 s Db 263 ,sf 27 s Sg 265 ,sf? 7.4 s Sg 266 ,sf? 21 s 1.4s Sg 263  0.3s ,sf? 0.9s Sg 261 ,ec 0.23 s Sg 260 ,sf 3.6 ms Sg 259  0.48 s Sg 258 sf 2.9 ms Bh 261  11.8 ms Bh 264  440 ms Bh 262  102ms  8ms Db 256 ,sf 2.6 s Db 255 ,sf 1.6 s Bh 260  ? Hs 263  ? Hs 264 ,sf 0.45 ms Hs 265  0.8ms  1.7ms  Hs ms Hs 269   9.3 s Mt 266  1.7 ms Mt 268  70 ms Ds 267   3  s Ds 271  1.1ms  56 ms Ds 273  291  s 269  170  s Ds 272  1.6 ms  194  s  277  s Rf Ruther- fordium Db Dubnium Sg Seaborgium Bh Bohrium Hs Hassium Mt Meitnerium Ds N 166 Z Bh 266   1s Bh 267   17 s Hs ms  Sg 262 sf 6.9 ms Ds 270  0.1ms  6 ms Db 259,ec/sf? 0.5 s  Hs 270   3.6 s   87 ms   32 ms   0.48 s   100 ms   3.6 s   170 ms   0.72 s Mt 275   9.7 ms Mt 272   9.8 s Bh 271  Bh 268   16 h Db 267   73 m Db 290   30 ms   0.4 s  sf  2 ms Evidence for long-lived isotopes from 48 Ca induced fusion reactions on actinide targets (FLNR, published and unpublished data)  -Decay Spontaneous fission EC-Decay Darmstadtium, sf  7.9 s

- Half-lives of primary evaporation residues and their progenies: ms to h (Chemistry needs ≥ s) - Decay properties: mostly  -decay chains ending in a SF-nuclide (Problem: No link to known nuclides) - Maximum production cross sections  1 to 5 pb (3n and 4n channels). For 1 mg/cm 2 targets and 0.5 p  A beam approx. 0.6 to 3 atoms/day produced (Problem: UNILAC duty cycle, cw beam would enable approx. factor of 3 higher intensity at equal peak current)

The missing link: 287   5 s sf  3 min Hs 277 sf  10  min 285   10 min   1 min Ds 289   20 s   45 s 112   2.6 s sf  7.6 s Ds 292   53 ms 116 Rf 253 sf 48  s Rf 254 sf 23  s Rf 256 sf,  6.2  s Rf 257 ,ec 4.7s ,ec Rf 258 sf 13 ms Rf 259 ,sf 3.1 s Rf 260 sf 21 ms Rf 261  78 s Rf 262 sf 47ms 1.4s Rf 255 ,sf 0.8s ,sf 1.4s2.1s sf Db 257 ,sf 1.3 s Db 258 ,ec 4.4 s Db 260 ,ec/sf? 1.5 s Db 261 ,sf 1.8 s Db 262 ,ec/sf? 34 s Db 263 ,sf 27 s Sg 265 ,sf? 7.4 s Sg 266 ,sf? 21 s 1.4s Sg 263  0.3s ,sf? 0.9s Sg 261 ,ec 0.23 s Sg 260 ,sf 3.6 ms Sg 259  0.48 s Sg 258 sf 2.9 ms Bh 261  11.8 ms Bh 264  440 ms Bh 262  102ms  8ms Db 256 ,sf 2.6 s Db 255 ,sf 1.6 s Bh 260  ? Hs 263  ? Hs 264 ,sf 0.45 ms Hs 265  0.8ms  1.7ms  Hs ms Hs 269   9.3 s Mt 266  1.7 ms Mt 268  70 ms Ds 267   3  s Ds 271  1.1ms  56 ms Ds 273  291  s 269  170  s Ds 272  1.6 ms  194  s  277  s Rf Ruther- fordium Db Dubnium Sg Seaborgium Bh Bohrium Hs Hassium Mt Meitnerium Ds N 166 Z Bh 266   1s Bh 267   17 s Hs ms  Sg 262 sf 6.9 ms Ds 270  0.1ms  6 ms Db 259,ec/sf? 0.5 s  Hs 270   3.6 s   87 ms   32 ms   0.48 s   100 ms   3.6 s   170 ms   0.72 s Mt 275   9.7 ms Mt 272   9.8 s Bh 271  Bh 268   16 h Db 267   73 m Db 290   30 ms   0.4 s  sf  2 ms  -Decay Spontaneous fission EC-Decay Darmstadtium, sf  7.9 s Hs chemistry, a tool to bridge the gap A. Türler et al.

- Half-lives of primary evaporation residues and their progenies: ms to h (Chemistry needs ≥ s) - Decay properties: mostly  -decay chains ending in a SF-nuclide (Problem: No link to known nuclides) - Maximum production cross sections  1 to 5 pb (3n and 4n channels). For 1 mg/cm 2 targets and 0.5 p  A beam approx. 0.6 to 3 atoms/day produced (Problem: UNILAC duty cycle, cw beam would enable approx. factor of 3 higher intensity at equal peak current)

S. Soverna January 2004

Standard enthalpies of gaseous mono- atomic elements Atomic number  H ° 298 [kcal/mol] B. Eichler, 1976 Conclusion: Elements 112 to 117 should be volatile noble metal-like elements Problem: Influence of relativistic effects?

Relativistic Extrapolations K.S. Pitzer, J. Chem. Phys. 63, 1032 (1975) V. Pershina et al., Chem. Phys. Lett., 365, 176 (2002) B. Eichler, Kernenergie 10, 307 (1976 ) B. Eichler, PSI Report 03-01, Villigen (2000) Noble gas like Volatile metal

How to experimentally determine a metallic character at a single atom level? → Determine interaction energy (adsorption enthalpy) with (noble*) metals, i.e. measure retention temperature * Easier to keep clean surface during experiment

isothermal chromatography Temperature [°C] Column length [cm] Temperature [°C] Yield [%] 50% T t Ret. = T 1/2 Gas flow highlow thermochromatography Temperature [°C] Column length [cm] Temperature [°C] Yield [%] T a high Gas flow low

R. Eichler et al.

Current interest: element 112 → Behaves E112 similar to Hg ? → Production: 238 U( 48 Ca;3n) (SF;T 1/2  3 min) → 2 chemistry experiments performed with evicence for: At FLNR: Isothermal chromatography on Au: E112 does not adsorb at room temp.  H a < 60 kJ/mol (A. Yakushev et al.) At GSI: Thermochromatography: E112 does not deposit on Au down to -90 °C  H a < 48 kJ/mol (S. Soverna et al.)

238 U( 48 Ca,3n)  20 s sf m  20 s EVR 286  20 s sf m  20 s EVR 286  20 s sf m  20 s EVR 286  20 s sf m  20 s EVR 286 VASSILISSA E* 33 MeV E* 35 MeV Oganessian et al., 1999 & in press

Current interest: element 112 → Behaves E112 similar to Hg ? → Production: 238 U( 48 Ca;3n) (SF;T 1/2  3 min) → 2 chemistry experiments performed with evicence for: At FLNR: Isothermal chromatography on Au: E112 does not adsorb at room temp.  H a < 60 kJ/mol (A. Yakushev et al.) At GSI: Thermochromatography: E112 does not deposit on Au down to -90 °C  H a < 48 kJ/mol (S. Soverna et al.)

Ar +CH 4 mixture 48 Ca He inlet He outlet He Gas outlet Chemical isolation of Element 112 Target: U 3 O 8 - 2mg/cm 2 + Nd 2 O  g/cm 2 Beam: 48 Ca (262 MeV) 0.6 p  A Dose: 2.8x10 18 ; 8 SF detected in ion.chamber in coincidence with 1 to 3 neutrons

Current interest: element 112 → Behaves E112 similar to Hg ? → Production: 238 U( 48 Ca;3n) (SF;T 1/2  3 min) → 2 chemistry experiments performed with evicence for: At FLNR: Isothermal chromatography on Au: E112 does not adsorb at room temp.  H a < 60 kJ/mol (A. Yakushev et al.) At GSI: Thermochromatography: E112 does not deposit on Au down to -90 °C  H a < 48 kJ/mol (S. Soverna et al.)

oven (1000 °C) Ta-/Ti-getter quartz wool filter oven (850 °C) ~10 m PFA-capillary 48 Ca-Beam recoil chamber rotating 238 U-target (1.6 mg cm -2 ) PIN-dioden oppositer thermostat surface N 2 (liq.) (-196 °C) (+35 °C) a S. Soverna January 2004

Experiment GSI February-March U( 48 Ca, 3n) (SF, 3min)

Both experiments not conclusive, because → Detection of SF activity not specific to assign it to a given (isotope of an) element. → Fission fragment energies too low (FLNR: ion. chamber; GSI: PIN- diodes)

Current effort: focus on  - decaying nuclides

V. Utyonkov, priv. comm. Feb Ca DGFRS/FLNR

Device 2004 Ar/He carrier gas loop (v=10 l) Ar - refill 48 Ca beam Recoil chamber (volume approx.10 cc Buffer Getter oven Pressure gauge / MFC 4-  COLD, 1 side gold All metal Rn Trap Mass flow controller

Requirements for future SHE chemistry experiments (e.g. Z=114) - Fast (separation time approx. 1 s) - Separation of transfer products prior to chemistry set-up: ChemSep - Chemistry behind a ChemSep - Beam dose of ≥ required for approx. 1 month experiments: 1 p  A average beam intensity! cw-LINAC; Novel target technology (stable compounds, liquid metal targets)

DGFRS 1 x Ds 179 sf 0.31 s  20 s EVR 290  20 s s  9.5  20 s s  Pu( 48 Ca,5n) E* 52 MeV 242 Pu( 48 Ca,3n)  20 s EVR 290 Ds s  9.7  20 s s  9.5  20 s Hs ms  9.3  20 s sf Sg m  20 s s  10 Ds 179 sf 0.2 s  20 s EVR 290  20 s s  9.5  20 s s  x1 x E* 40 MeV E* MeV 245 Cm( 48 Ca,2n)  20 s s  20 s EVR 293  9.5  20 s ms   20 s s  10 Ds 179 sf 0.2 s 2 x E* 35 MeV

Reqiurements for future SHE chemistry experiments - Fast (separation time approx. 1 s) - Separation of transfer products prior to chemistry set-up: ChemSep - Chemistry behind a ChemSep - Beam dose of ≥ required for approx. 1 month experiments: 1 p  A average beam intensity! cw-LINAC; Novel target technology (stable compounds, liquid metal targets)

220 Rn 48 Ca Cm H.W. Gäggeler et al., Phys. Rev. C33, 1983 (1986) Transfer reaction products!

Requirements for future SHE chemistry experiments - Fast (separation time approx. 1 s) - Separation of transfer products prior to chemistry set-up: ChemSep - Chemistry behind a ChemSep - Beam dose of ≥ required for approx. 1 month experiments: 1 p  A average beam intensity! cw-LINAC; - Novel target technology (stable compounds, liquid metal targets)

A recoil/gas chemistry chamber at the Berkeley Gas-filled Separator (BGS)

Hot-catcher coupled to vacuum thermochromatography set-up Induction heating Hot Catcher R. Eichler, Qin Zhi 

R.Eichler, Qin Zhi

Requirements for future SHE chemistry experiments - Fast (separation time approx. 1 s) - Separation of transfer products prior to chemistry set-up: ChemSep - Chemistry behind a ChemSep - Novel target technology (stable compounds, liquid metal targets) - Beam dose of ≥ required for approx. 1 month experiments: 1 p  A average beam intensity! cw-LINAC;

Suggested application: liquid U/Mn (80/20) at 700 °C

Requirements for future SHE chemistry experiments - Fast (separation time approx. 1 s) - Separation of transfer products prior to chemistry set-up: ChemSep - Chemistry behind a ChemSep - Novel target technology (stable compounds, liquid metal targets) - Beam dose of ≥ required for approx. 1 month experiments: 1 p  A average beam intensity! (cw-LINAC)