FLEROV LABORATORY of NUCLEAR REACTIONS
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Transcript FLEROV LABORATORY of NUCLEAR REACTIONS
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
CHART of the NUCLIDES
Decay of 268 Db observed with
Dubna Gas-filled Recoil Separator
in 243Am + 48Ca Reaction
288
a1
284
EL = 248 MeV
a2
280
a3
276
a4
272
a5
R
Bh
Mt
111
115
10.46 MeV
125 ms
113
10.00 MeV
0.69 s
9.75 MeV
5.2 s
9.71 MeV
1.03 s
9.02 MeV
14.14 s
268
Db
SF
205 MeV
23.1 hr
Yu. Oganessian et al.,
Phys. Rev. C 69, 021601(R) 2004
243Am
+
3n 288
5a 268
48Ca
115
Db
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
16+19
hr
-6
-
Cross section
+4.8
2.7-1.6
pb
-
3.1017 / day
-
1-2 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 48Ca + 243Am reaction
June 2004, FLNR, DUBNA
FLNR JINR (Dubna, Russia)
PSI, University of Bern (Switzerland)
IPN (Orsay, France)
LLNL (Livermore, USA)
CHEMICAL IDENTIFICATION of the Db
Electronic ground-state configuration:
[Rn] 5d146d37s2 – group 5 elem. Periodic Table
(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 HNO3 / HF
into
MIBK
(Db
Ta, Db336
Nb)
HCl, HF
– Aliquat
system
HCl Pa > Nb Db > Ta
HF Db Nb Ta >> Pa
[DbF7]2HF – Dowex50 (Cation-exchange) System
2Ac+3(kd104); NbF
7
EXPERIMENT SCHEME
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 100150 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 855%)
(177Ta 75 5%)
48Ca
+
243Am
1
Beam
Dose
Ebot+Etop+ 0 n (t,c)
tdetect
hr
tmeasurement
hr
20
2,51017
120+126+21n (5;64)
20
429
2 (13.06)
22
3,71017
̶ +86+11n (57)
74
186
3 (14.06)
22
3,41017
131+124+110n (3)
116+122+210n (8;16)
15
72
385
104+120+110n (2)
97+125+110 n (151)
100+128+110n (89)
22
29
51
117+118+210 n (6,98)
108+107+310 n (4,31,43)
110+104+010n
1
--+76+20 n (6,41)
6
9
15
68
N Sample
(data)
tirr
hr
1 (12.06)
4 (15.06)
5 (17.06)
22
38
2,91017
6,71017
0
0
358
861
6 (18.06)
23
3,91017
120+114+210n (2,2)
39
933
7 (19.06)
22
3,61017
-
-
957
8 (21.06)
45
7,41017
119+110+201n (5;33)
118+105+210 n (72,165)
65+58+310n (12,19,29)
5
93
174
910
3,4.1018
15 events
252Cf
252Cf
and
254Cf
- 2,645 y (α)
(3,09%- SF)
254Cf
- 60,5 d (SF)
(0,31% - α)
• sample 9 (3 . 1017) - SSD on the catcher surface
(without chemistry)
• 2 tracks/ day ( 72 days)
• Kseparation ≈ 105 (preliminary experiments with tracers)
≥ 8.103 ( samples)
• SF (Actinides, incl. 264Lr) < 0.1 %
Number of neutrons registered by 3He detectors per SF-decay
(without taking into account the detector efficiency)
The Periodic Table
CHART of the NUCLIDES
17
243Am
+
3n 288
5a 268
48Ca
115
Db
“Physical” experiment4
“Chemical” experiment
Kinematic separator
Radiochemical separation
≈ 40%
≈ 80%
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 MeV
247 MeV
Total ion beam dose (ions)
4.5·1018
3.4·1018
0.3 mg/cm2
1.2 mg/cm2
3
15
~ 2,7+4,8-1,6 pb
4,2+1,6-1,2 pb
16+19-7 hours
32+11 -7 hours
~ 230 MeV
~ 235 MeV
-
4.2
Separation method
Separation efficiency
Registration
Thickness of
243Am
target
The number of events of the decay
observed at experiment
Cross section of producing the mother
nucleus of element 115
Half-life of 105 element
Total kinetic energy of fission fragments
( TKE )
The average neutron multiplicity per
fission
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
243Am+48Ca consists of 5 sequential a-transitions resulting in the
formation of the long-lived nucleus of element 105 leading to
spontaneous fission. A hypothesis of the possible a-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 243Am+48Ca
FUTURE EXPERIMENTS
Determination of the mass of Super Heavy Nuclei
MASHA Off-line
243Am
48Ca
3n
+
(Chemistry –
IS
+ MS
288115
5a
X
Db)
105
DbCl5 Db A = 268
(5 group, A = 268)
268
105
Db
288
115
268Db