CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca Am reaction CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca Am reaction The 97 th session of the JINR Scientific Council, January 2005

CHART of the NUCLIDES

R Decay of 268 Db observed with Dubna Gas-filled Recoil Separator in 243 Am + 48 Ca Reaction E L = 248 MeV Yu. Oganessian et al., Phys. Rev. C 69, (R) MeV 125 ms 1  MeV 5.2 s Mt  9.71 MeV 1.03 s Bh  0.69 s  10. MeV hr SF 205 MeV s 5  9.02 MeV Db 268

DGFRSCHEMISTRY 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 Events Number 3- Decay Moda SFSF Half Life hr - Cross section pb Am + 48 Ca   268 Db 3n 5555 / day event Dmitriev S., Oganessian Yu., Itkis M., TAN 03, November 16-20, 2003, Napa, California

CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca Am reaction CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca Am reaction June 2004, FLNR, DUBNA FLNR JINR (Dubna, Russia) PSI, University of Bern (Switzerland) LLNL (Livermore, USA) IPN (Orsay, France)

CHEMICAL IDENTIFICATION of the Db [DbF 7 ] 2- HF – Dowex50 (Cation-exchange) System Ac +3 (k d  10 4 ); NbF 2- 7 Electronic ground-state configuration: (Nb – Ta – Db) What we know about aqueous phase chemistry of Db? Db is adsorbed on glass surface from nitric acid (like Nb and Ta) Db is not extract from 3.8 M HNO 3 / HF into MIBK (Db  Ta, Db  Nb) HCl, HF – Aliquat 336 system HCl  Pa > Nb  Db > Ta HF  Db  Nb  Ta >> Pa [Rn] 5d 14 6d 3 7s 2 – group 5 elem. Periodic Table

EXPERIMENT SCHEME

OUTLINE of the EXPERIMENT OUTLINE of the EXPERIMENT  Irradiation of 243 Am-target with 48 Ca-ions (accumulation of the EVR by copper catcher) catcher)  Removal of a Catcher from the target system and its transportation to the Radio.Chem.Lab. Radio.Chem.Lab.  Cleaning of the catcher surface from 243 Am-aerosol particles by a cotton saturated with C 2 H 5 OH saturated with C 2 H 5 OH  Taking off thin layer of Cu (7-10  100  150 mg Cu) on the micro-lathe  Dissolution of the Cu-cuttings in HNO 3 conc.  Addition of the La 3+ (0.7 mg), tracers ( 92m Nb, 177 Ta, 167 Tm, 169 Yb) and carriers Nb, Ta (1  g) Nb, Ta (1  g)  Precipitation of La(OH) 3 by NH 4 OH (La, Nb, Ta, Db, Ac – precipitate; Cu-solution) – 3 times (Nb, Ta  99%) Cu-solution) – 3 times (Nb, Ta  99%)  Dissolution of the La(OH) 3 in 2M HNO 3  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/cm 2 ) -  3 hr ( 92m Nb  85  5%) ( 92m Nb  85  5%) ( 177 Ta  75  5%) ( 177 Ta  75  5%)

15 events 48 Ca Am N Sample (data) t irr hr Beam Dose E bot +E top + 1 n (t,  c) t detect hr t measurement hr 1 (12.06) 20 2,5  n (5;64) (13.06) 22 3,7  ̶ n (57) (14.06) 22 3,4  n (3) n (8;16) (15.06) 22 2,9  n (2) n (151) n (89) (17.06) 38 6,7  n (6,98) n (4,31,43) n n (6,41) (18.06) 23 3,9  n (2,2) (19.06) 22 3,6  (21.06) 45 7,4  n (5;33) n (72,165) n (12,19,29)  3,

252 Cf and 254 Cf 252 Cf - 2,645 y (α) (3,09%- SF) (3,09%- SF) 254 Cf - 60,5 d (SF) (0,31% - α) (0,31% - α) sample 9 ( ) - SSD on the catcher surface sample 9 ( ) - SSD on the catcher surface (without chemistry) (without chemistry) 2 tracks/ day ( 72 days) 2 tracks/ day ( 72 days) K separation ≈ 10 5 (preliminary experiments with tracers) K separation ≈ 10 5 (preliminary experiments with tracers) ≥ ( samples) SF (Actinides, incl. 264 Lr) < 0.1 % SF (Actinides, incl. 264 Lr) < 0.1 %

Number of neutrons registered by 3He detectors per SF-decay (without taking into account the detector efficiency) (without taking into account the detector efficiency)

The Periodic Table

17 CHART of the NUCLIDES

243 Am + 48 Ca   268 Db 3n 5555 “Physical” experiment 4 “Chemical” experiment Separation methodKinematic separatorRadiochemical separation Separation efficiency≈ 40%≈ 80% Registration Decay chains of nuclei with Z=115 SF nuclei with Z=105 Energy of 48 Ca- ion beam at the middle of target layer 246 MeV247 MeV Total ion beam dose (ions)4.5· ·10 18 Thickness of 243 Am target 0.3 mg/cm mg/cm 2 The number of events of the decay observed at experiment 315 Cross section of producing the mother nucleus of element 115 ~ 2,7 +4,8 -1,6 pb4,2 +1,6 -1,2 pb Half-life of 105 element hours hours Total kinetic energy of fission fragments ( TKE ) ~ 230 MeV~ 235 MeV The average neutron multiplicity per fission -4.2

Conclusion Conclusion  The properties of the isotope 268 Db 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 243 Am+ 48 Ca 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 243 Am+ 48 Ca

FUTURE EXPERIMENTS  Determination of the mass of Super Heavy Nuclei MASHA Off-line MASHA Off-line (Chemistry – X Db) Am + 48 Ca   268 Db 55553n (5 group, A = 268) DbCl 5  Db  A = 268 MS IS IS Db 