1. CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca + 243 Am reaction CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca + 243 Am reaction The 97 th session of the JINR Scientific Council, 20-21 January 2005

2. CHART of the NUCLIDES

3. 115 288 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, 021601(R) 2004 10.46 MeV 125 ms 1  113 284 9.75 MeV 5.2 s Mt 276 3  9.71 MeV 1.03 s Bh 272 4  0.69 s 111111 280 2  10. MeV00 23.1 hr SF 205 MeV 14.14 s 5  9.02 MeV Db 268

4. 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 4.3. 10 18 - Events Number 3- Decay Moda SFSF Half Life 16 +19 hr - Cross section 2.7 +4.8 pb - 243 Am + 48 Ca  288 115  268 Db 3n 5555-1.6 -6 3. 10 17 / day - 1-2 event Dmitriev S., Oganessian Yu., Itkis M., TAN 03, November 16-20, 2003, Napa, California

5. CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca + 243 Am reaction CHEMICAL IDENTIFICATION of the element Db as decay product of the element 115 in the 48 Ca + 243 Am reaction June 2004, FLNR, DUBNA FLNR JINR (Dubna, Russia) PSI, University of Bern (Switzerland) LLNL (Livermore, USA) IPN (Orsay, France)

6. 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

7. EXPERIMENT SCHEME

9. 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%)

11. 15 events 48 Ca + 243 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  10 17 120+126+2 1 n (5;64) 20429 2 (13.06) 22 3,7  10 17 ̶ +86+1 1 n (57) 74186 3 (14.06) 22 3,4  10 17 131+124+1 1 n (3) 116+122+2 1 n (8;16) 1572385 4 (15.06) 22 2,9  10 17 104+120+1 1 n (2) 97+125+1 1 n (151) 100+128+1 1 n (89) 222951358 5 (17.06) 38 6,7  10 17 117+118+2 1 n (6,98) 108+107+3 1 n (4,31,43) 110+104+0 1 n -- +76+2 1 n (6,41) 691568861 6 (18.06) 23 3,9  10 17 120+114+2 1 n (2,2) 39933 7 (19.06) 22 3,6  10 17 --957 8 (21.06) 45 7,4  10 17 119+110+2 1 n (5;33) 118+105+2 1 n (72,165) 65+58+3 1 n (12,19,29) 593174910 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  3,4. 10 18

12. 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 (3. 10 17 ) - SSD on the catcher surface sample 9 (3. 10 17 ) - 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) ≥ 8. 10 3 ( samples) SF (Actinides, incl. 264 Lr) < 0.1 % SF (Actinides, incl. 264 Lr) < 0.1 %

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

16. The Periodic Table

17. 17 CHART of the NUCLIDES

18. 243 Am + 48 Ca  288 115  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 3.4·10 18 Thickness of 243 Am target 0.3 mg/cm 2 1.2 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 element16 +19 -7 hours 32 +11 -7 hours Total kinetic energy of fission fragments ( TKE ) ~ 230 MeV~ 235 MeV The average neutron multiplicity per fission -4.2

19. 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

20. FUTURE EXPERIMENTS  Determination of the mass of Super Heavy Nuclei MASHA Off-line MASHA Off-line (Chemistry – X Db) 105 243 Am + 48 Ca  288 115  268 Db 55553n (5 group, A = 268) DbCl 5  Db  A = 268 MS IS IS + 268 Db  288 115 105