1 Transuranium elements Background Methods Extractions with Organic Ligands Search for New Isotope

2 Np synthesis Neptunium was the first synthetic transuranium element of the actinide series discovered isotope 239 Np was produced by McMillan and Abelson in 1940 at Berkeley, California bombarding uranium with cyclotron-produced neutrons  238 U(n,  ) 239 U, beta decay of 239 U to 239 Np (t 1/2 =2.36 days) Chemical properties unclear at time of discovery  Actinide elements not in current location  In group with W Chemical studies showed similar properties to U First evidence of 5f shell Macroscopic amounts 237 Np  238 U(n,2n) 237 U *Beta decay of 237 U  10 microgram

3 Pu synthesis Plutonium was the second transuranium element of the actinide series to be discovered The isotope 238 Pu was produced in 1940 by Seaborg, McMillan, Kennedy, and Wahl deuteron bombardment of U in the 60-inch cyclotron at Berkeley, California  238 U( 2 H, 2n) 238 Np *Beta decay of 238 Np to 238 Pu Oxidation of produced Pu showed chemically different 239 Pu produced in 1941 Uranyl nitrate in paraffin block behind Be target bombarded with deuterium Separation with fluorides and extraction with diethylether Eventually showed isotope undergoes slow neutron fission

4 Am and Cm discovery Problems with identification due to chemical differences with lower actinides Trivalent oxidation state 239 Pu( 4 He,n) 242 Cm Chemical separation from Pu Identification of 238 Pu daughter from alpha decay Am from 239 Pu in reactor Also formed 242 Cm Difficulties in separating Am from Cm and from lanthanide fission products

5 Bk and Cf discovery Required Am and Cm as targets Needed to produce theses isotopes in sufficient quantities  Milligrams Am from neutron reaction with Pu Cm from neutron reaction with Am 241 Am( 4 He,2n) 243 Bk Cation exchange separation 242 Cm( 4 He,n) 245 Cf Anion exchange

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7 Einsteinium and Fermium Debris from Mike test 1 st thermonuclear test New isotopes of Pu 244 and 246  Successive neutron capture of 238 U Correlation of log yield versus atomic mass Evidence for production of transcalifornium isotopes Heavy U isotopes followed by beta decay Ion exchange used to demonstrate new isotopes

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9 Md and No discovery 1 st atom-at-a-time chemistry 253 Es( 4 H,n) 256 Md Required high degree of chemical separation Use catcher foil Recoil of product onto foil Dissolved Au foil, then ion exchange No controversy Expected to have trivalent chemistry 1 st attempt could not be reproduced  Showed divalent oxidation state 246 Cm( 12 C,4n) 254 No  Alpha decay from 254 No  Identification of 250 Fm daughter using ion exchange

10 Lr discovery 249, 250, 251 Cf bombarded with 10,11 B New isotope with 8.6 MeV, 6 second half life Identified at 258 Lr

11 Isotopes of Rf Mass NumberHalf LifeDecay Mode and  Energies (MeV) 253?­1.8 sSF,  254?0.5 msSF sSF 2567 msSF,  (8.81) s  (8.77, 9.01, 8.95, 8.62) msSF s , SF (8.77, 8.86) msSF s  (8.29) msSF

12 Previous Chemistry 1966 Zvara et al. 242 Pu( 22 Ne,4n) 260 Ku 114 Mev 12 observed events Formation of Ku tetrachloride in the gas phase 1970 Silva et al. 248 Cm( 18 O,5n) 261 Rf 92 MeV 17 observed events Cation column extraction with Zr and Hf 1980 Hulet et al. 248 Cm( 18 O,5n) 261 Rf 98 MeV 6 observed events Al-336 Column (0.25M in o-xylene) 12M HCl: removes actinides 6M HCl: Zr, Hf and Rf elute

13 Why Study the Chemistry of Rf? Test validity of the Extrapolations of the Periodic Table Determine the Influence of Relativistic Effects on Chemical Properties Help to Predict the Chemical Properties of the Heavier Elements Determine Nuclear Properties of the Heaviest Elements

14 Difficulties Chemistry of the Heaviest Elements Low production rates Short half-lives Large interference from other activities Capabilities 88-inch cyclotron: high intensity LHI beams Facilities for and expertise in fabrication and irradiation of extremely radioactive targets Facilities for and expertise in fast radiochemical and detection techniques

Rf Production 248 Cm( 18 O, 5n) 261 Rf;  5 nb Production Rate = 1.1 min Detection Rate = 1 event / 5 exps. = 1 event/ 7 minutes Transport to chemistry hood via gas-jet Target: 0.5 mg/cm 2 ; Beam: 0.5 p  A

16 Target System

Rf Decay 261 Rf 65 s 257 No 8.29 MeV 8.22 MeV 8.27 MeV 8.32 MeV   26 s

Rf Spectra

19 Rf Chemical Separation Liquid-Liquid Extraction System Requirements: Rapid Phase Separation Quick kinetics (< 10 seconds) Clean separation from actinides Actinides are formed by transfer reactions Organic phase must evaporate quickly and cleanly Required for good alpha spectroscopy Pick up activity with 10 µL aqueous phase Add to 20 µL organic phase in a 1 mL centrifuge tube Mix for 5 seconds Centrifuge for 5 seconds Remove and evaporate organic phase on a counting plate Place plate on a PIPS detector for  and SF counting Time of chemistry is about 1 minute Repeat every 90 seconds Up to 1000 extractions per day

20 Fast Chemical Extraction Procedure Pick up activity with 10 µL aqueous phase Add to 20 µL organic phase in a 1 mL centrifuge tube Mix for 5 seconds Centrifuge for 5 seconds Remove and evaporate organic phase on a counting plate Place plate on a PIPS detector for  and SF counting Time of chemistry is about 1 minute Repeat every 90 seconds Up to 1000 extractions per day

21 Isotopes Homolog tracer Study 0.1 to 0.5 mL Aqueous and Organic phases Mix phase in a 5 mL centrifuge tube for 1 minute Centrifuge for 30 seconds Separate Phases and count Alpha or Gamma Spectroscopy to determine % Extracted Isotopes On line at 88-inch cyclotron Rf, 162,169 Hf Tracers 238 Pu, 228 Th, 95 Zr, 172 Hf, 152 Eu

22 Organic Extractants Triisooctylamine (C 8 H 17 ) 3 NAnionic Species (TIOA) Tributyl Phophate Neutral Species (TBP) Thenoyltrifluoroactone Chelation (TTA) (CH 3 (CH 2 ) 3 O) 3 PO Organic Soluble Low Boiling Point Chemically Specific

23 Experimental Conditions Organic Phase: Ligand in Benzene 0.1, 1.0 M for TIOA 0.25 M for TBP 0.5 M for TTA Aqueous Phase: For TIOA : 12 M HCl For TBP: HCl : 8 to 12 M Cl : 8 to 12 M with [H ] = 8 M H : 8 to 12 M with [Cl ]=12 M For TTA0.24, 0.10, and 0.05 M HCl

Rf TIOA Extraction Data [TIOA]MExtraction# Events# Experiments (%) Extraction Similar to Group 4 Anionic Species Formation Results Similar to Anion Exchange Loss Due to Evaporation

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27 TBP Results Similar to Pu Extraction Anionic Species Formation Deviation from Group 4 Elements Trends Towards Actinides log Keq for Rutherfordium with TTA Solutionlog Kdlog Keq 0.24 M HCl M HCl Ave Values between Th and Pu

28 TTA Extraction

29 Rutherfordium Hydrolysis Constants XYlog Kxy Values between Th and Pu/Hf

30 Ionic Radius for Tetravalent Rutherfordium Coordination NumberIonic Radius (pm) For 6 Coordinate Previous Experimental Data 89 pm Theoretical Calculations pm

31 Search for Rf 263 Previous Work Cm( Ne, , 3n) Rf No events detected Half-life upper limit of 20 minutes Cm( O, 3n) Rf 92 MeV on target Cross Section Estimate = 300 pb Production Reaction

32 Alpha Half-Life Range From Masses Assumes Ground State to Ground State Transition Mass ModelE  (MeV)t (sec.) Satpathy Möller and Nix /2

33 Log =6 ft SatpathyMöller and Nix Rf Lr EC Half-life Seconds EC 263 EC Half-life estimate

34 Fission Half-Life Estimate For 159th neutron Fm Hinderance Factor ­ 4000 SF t for Rf= 52 ms Estimate for Rf ­ 206 s 1/

35 Results 7 SF and no alpha events in Rf chemical fraction in 300 experiments Cross Section pb (300 pb Estimate) Half-life seconds (200 s Estimate from SF) Conclusions SF Dominate Decay Mode Möller and Nix Masses

36 Ceramic Plutonium Target Development for the MASHA Separator for the Synthesis of Element 114 A Pu ceramic target is being developed for the MASHA mass separator Range of energies as particle travels through target Ceramic must be capable of Tolerating temperatures up to 2000 ºC Reaction products must diffuse out of the target into an ion Low vapor pressure Experiments on MASHA will allow measurements that verify the identification of element 114 and provide data for future experiments on chemical properties of the heaviest elements.

37 Project Goals Develop Pu containing ceramic for target. (Sm,Zr)O 2-x ceramics are produced and evaluated Production of Pb (homolog of element 114) by the reaction of Ca on Sm Analysis on the feasibility of using a ZrO 2 -PuO 2 as a target for the production of element 114 Phases of the resulting Sm, Zr oxide ceramics are evaluated using XRD and subsequent data analysis along with microscopy and thermal analysis

38 MASHA Separator Mass Analyzer of Super Heavy Atoms on-line mass separator under development at the Flerov Laboratory of Nuclear Reactions at JINR Reaction products diffuse out of the heated, porous target and drift to an ion source ionized and injected into the separator The products impinge on a position-sensitive focal- plane detector array for mass measurement Initial tests will use surrogate products Element 114 experiments will be performed using ceramics containing 244 Pu to be irradiated by 48 Ca ions

39 MASHA Separator

40 Ceramic Target Range of particle energies in interaction with ceramics Different cross sections evaluated Sample entire excitation range Permits production of different isotopes of element 114

41 Candidate ceramics PuN, Pu 2 C 3, PuP, PuS, PuB, PuO 2 Oxide best candidate Pu solid solutions can be synthesized Various zirconia containing ceramics have been examined, including ZrO 2 -PuO 2 Properties of ZrO 2 -PuO 2 have been examined by experiment and by models (Pu,Zr)O 2 based targets should have suitable properties for the production of element 114  Ease of synthesis  Single phase over a large range  Ability to design porous ceramic  Low Pu volatility Start with Sm oxides to produce Pb (homolog of element 114)

42 Ceramic Composition #SmO 1.5 ZrO 2 Zn StearatePEG Mol % OxidesWt. % additive

43 XRD Analysis

44 Element 114 Conclusions Candidates for the MASHA target are currently being prepared and characterized. On-line tests with MASHA will begin with surrogate Sm targets, but subsequent irradiations with 242 Pu and ultimately 244 Pu will be performed. Once the target is prepared and tested, experiments designed to measure the mass of element 114 will begin.