FLEROV LABORATORY of NUCLEAR REACTIONS

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CHEMICAL IDENTIFICATION of the element Db as
decay product of the element 115 in the 48Ca
243Am reaction
The 97th session of the JINR Scientific Council,
20-21 January 2005
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CHART of the NUCLIDES
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Decay of 268 Db observed with Dubna Gas-filled
Recoil Separator in 243Am 48Ca Reaction
EL 248 MeV
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DGFRS CHEMISTRY
Target Thickness 0.36 mg.cm-2 1.0 mg.cm-2
Energy Range 3.3 MeV 10 MeV
Transmission 35 ? 75 (expected)
Beam Dose 4.3.1018 -
Events Number 3 -
Decay Moda SF SF
Half Life 1619 hr -
Cross section 2.74.8 pb -
-6
-1.6
3.1017 / day - 1-2 event
Dmitriev S., Oganessian Yu., Itkis M., TAN 03,
November 16-20, 2003, Napa, California
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CHEMICAL IDENTIFICATION of the element Db as
decay product of the element 115 in the 48Ca
243Am reaction
June 2004, FLNR, DUBNA
FLNR JINR (Dubna, Russia)
PSI, University of Bern (Switzerland)
IPN (Orsay, France)
LLNL (Livermore, USA)
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CHEMICAL IDENTIFICATION of the Db
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EXPERIMENT SCHEME
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OUTLINE of the EXPERIMENT

• Irradiation of 243Am-target with 48Ca-ions
  (accumulation of the EVR by copper
• catcher)
• Removal of a Catcher from the target system and
  its transportation to the
• Radio.Chem.Lab.
• Cleaning of the catcher surface from
  243Am-aerosol particles by a cotton
• saturated with C2H5OH
• Taking off thin layer of Cu (7-10 ??100?150 mg
  Cu) on the micro-lathe
• Dissolution of the Cu-cuttings in HNO3 conc.
• Addition of the La3 (0.7 mg), tracers (92mNb,
  177Ta, 167Tm, 169Yb) and carriers
• Nb, Ta (1 ?g)
• Precipitation of La(OH)3 by NH4OH (La, Nb, Ta,
  Db, Ac precipitate
• Cu-solution) 3 times (Nb, Ta ?99)
• Dissolution of the La(OH)3 in 2M HNO3
• Sorbtion of La, Ac, Nb, Ta, Db on Dowex 50
  (cation-exchange resin)
• Elution of group 5 elements (Nb, Ta, Db) with 2
  ml 1M HF
• Evaporation of the solution to 0.1 ml
• Pipetting of the 0.1 ml solution on a PE-foil
  (40mkg/cm2) - ??3 hr
• 
  
  (92mNb ? 85?5)
• 
  
  (177Ta ? 75 ? 5)

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48Ca 243Am
N Sample (data) tirr hr Beam Dose EbotEtop 1n (t,?c) tdetect hr tmeasurement hr
1 (12.06) 20 2,5?1017 12012621n (564) 20 429
2 (13.06) 22 3,7?1017 ? 8611n (57) 74 186
3 (14.06) 22 3,4?1017 13112411n (3) 11612221n (816) 15 72 385
4 (15.06) 22 2,9?1017 10412011n (2) 9712511n (151) 10012811n (89) 22 29 51 358
5 (17.06) 38 6,7?1017 11711821n (6,98) 10810731n (4,31,43) 11010401n --7621n (6,41) 6 9 15 68 861
6 (18.06) 23 3,9?1017 12011421n (2,2) 39 933
7 (19.06) 22 3,6?1017 - - 957
8 (21.06) 45 7,4?1017 11911021n (533) 11810521n (72,165) 655831n (12,19,29) 5 93 174 910
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
? 3,4.1018
15 events
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252Cf and 254Cf
254Cf - 60,5 d (SF) (0,31 - a)
252Cf - 2,645 y (a) (3,09- SF)
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Number of neutrons registered by 3He detectors
per SF-decay (without taking into account the
detector efficiency)
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The Periodic Table
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CHART of the NUCLIDES
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Physical experiment4 Chemical experiment
Separation method Kinematic separator Radiochemical separation
Separation efficiency 40 80
Registration Decay chains of nuclei with Z115 SF nuclei with Z105
Energy of 48 Ca-ion beam at the middle of target layer 246 MeV 247 MeV
Total ion beam dose (ions) 4.5?1018 3.4?1018
Thickness of 243Am target 0.3 mg/cm2 1.2 mg/cm2
The number of events of the decay observed at experiment 3 15
Cross section of producing the mother nucleus of element 115 2,74,8-1,6 pb 4,21,6-1,2 pb
Half-life of 105 element 1619-7 hours 3211 -7 hours
Total kinetic energy of fission fragments ( TKE ) 230 MeV 235 MeV
The average neutron multiplicity per fission - 4.2
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• Conclusion
• The properties of the isotope 268Db produced in
  the decay chain of element 115 using the
  gas-filled recoil separator agree by all measured
  parameters with the data of the present chemical
  experiment on the determination of its atomic
  number.
• The decay chain of element 115 synthesized in
  the reaction 243Am48Ca consists of 5 sequential
  ?-transitions resulting in the formation of the
  long-lived nucleus of element 105 leading to
  spontaneous fission. A hypothesis of the possible
  ?-decay of the Db nucleus has been totally
  rejected by the conditions of chemical separation
  of the reaction products in this experiment.
• Thus, the data from the present experiment are
  the independent evidence for the synthesis of
  element 115 as well as element 113 in the
  reaction 243Am48Ca

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FUTURE EXPERIMENTS

• Determination of the mass of Super Heavy Nuclei

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