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6th China-Japan Joint Nuclear Physics Symposium Shanghai, China, May 17, 2006. Chemical studies of the transactinide elements at JAEA. Y. Nagame Advanced Science Research Center Japan Atomic Energy Agency (JAEA). Z ≥ 104: transactinide elements superheavy elements. - PowerPoint PPT Presentation
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Chemical studies of the transactinide elements at JAEA
Y. NagameAdvanced Science Research CenterJapan Atomic Energy Agency (JAEA)
6th China-Japan Joint Nuclear Physics SymposiumShanghai, China, May 17, 2006
Periodic table of the elementsPeriodic table of the elements
1 181 2
2 13 14 15 16 173 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18
3 4 5 6 7 8 9 10 11 1219 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 118
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
118
Al
Ni Cu Zn Ga
Si P S
H
Li
Na Mg
He
Be B NeFONC
Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ge As Se Br Kr
Rb XeITeSbSnInCd
Cs Ba La
MoNbZrY
Ta W
Sr
RnHg Tl Pb Bi AtPo
PdRhRuTc
Hf Re
Ag
116
Os Ir Pt Au
113 115
Lu
Mt
Tb Dy Ho ErEu
Rg 112 114
Lanthanides
DsHsDb Sg BhFr Ra Ac Rf
Ac ThActinides
YbLa Pr Nd Pm Sm GdCe Tm
No LrAm BkCm Cf Es FmPa U Np MdPu
Z ≥ 104: transactinide elements superheavy elements
Heavy element nuclear chemistry Heavy element nuclear chemistry at JAEAat JAEA
1. Chemical properties of the transactinide elements (Z 104) - Liquid-phase chemistry of Rf and Db2. Nuclear properties of heavy nuclei (Z 100) - spectroscopy of No (Z = 102) and Rf (Z = 104)
3. Nuclear fission of heavy nuclei (Z 100) - Fission modes in heavy nuclei
Contents
1. Introduction Chemical studies of the transactinide elements Relativistic effects in chemical properties of heavy elements Atom-at-a-time chemistry2. Chemical studies of element 104 (Rf) at JAEA Production of Rf Characteristic chemical properties of Rf based on an atom-at-a-time scale Fluoride complex formation of Rf3. Conclusion
1. Introduction
Objectives:
1. Basic chemical properties ionic charge, radius, redox potential, complex formation, volatility, etc.
2. Architecture of the Periodic table of the elements Periodicities of the chemical properties
3. Relativistic effects in chemical properties
Chemical studies of the transactinide elements
Relativistic effects (1)
General: increase of the mass with increasing velocity
At heavy elements: Increasing nuclear charge plays as the “accelerator” of the velocity of electrons.
Electrons near the nucleus are attracted closer to the nucleus and move there with high velocity. mass increase of the inner electrons and the contraction of the inner electron orbitals (Bohr radius)
Direct relativistic effects
mm0
(1 (v /c)2
aB 2
me2 2
m0e2 1 (v c)2 aB
0 1 (v c)2
Relativistic effects (2)
Electrons further away from the nucleus are better screened from the nuclear charge by the inner electrons and consequently the orbitals of the outer electrons expand. Indirect relativistic effects
It is expected that transactinide elements would show a drastic rearrangement of electrons in their atomic ground states, and as the electron configuration is responsible for the chemical behavior of elements, such relativistic effects can lead to surprising chemical properties.
Increasing deviations from the periodicity of chemical properties based on extrapolation from lighter homologues in the Periodic table are predicted.
Atom-at-a-time chemistryAtom-at-a-time chemistryThe transactinide elements must be produced at accelerators using reactions of heavy-ion beams with heavy target materials.
Because of the short half-lives and the low production rates of the transactinide nuclides, each atom produced decays before a new atom is synthesized.
Any chemistry to be performed must be done on an "atom-at-a-time" basis.
Rapid, very efficient and selective chemical procedures are indispensable to isolate desired transactinides.
Repetitive experiments
2. Chemical studies of rutherfordium
(Rf, Z = 104) at JAEA
Experimental approach to Rf chemistryExperimental approach to Rf chemistry
1 181 2
2 13 14 15 16 173 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18
3 4 5 6 7 8 9 10 11 1219 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 118
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103
Pa U Np MdPu No LrAm BkCm Cf Es Fm
YbLa Pr Nd Pm Sm GdCe Tm
Ac ThActinides
Lanthanides
DsHsDb Sg BhFr Ra Ac Rf
Lu
Mt
Tb Dy Ho ErEu
Rg 112 114
Hf Re
Ag
116
Os Ir Pt Au
113 115
PdRhRuTc
RnHg Tl Pb Bi AtPoCs Ba La
MoNbZrY
Ta W
Sr
Br Kr
Rb XeITeSbSnInCd
Co Ge As Se
Cl Ar
K Ca Sc Ti V Cr Mn Fe
He
Be B NeFONC
H
Li
Na Mg
118
Al
Ni Cu Zn Ga
Si P S
Increasing deviations from the periodicity of the chemical properties based on extrapolations from the lighter homologues are predicted.
Experimental approach should involve detailed comparison of the chemical properties of the transactinides with those of their lighter homologues under identical conditions.
We have investigated the chemical properties of Rf together with the lighter homologues Zr and Hf under the same on-line experiments.
Schematic flow of the experiment
Collection
Dissolution &Complex formation
He cooling gas
18O beam
HAVAR window2.0 mg/cm2
248Cm target
Beam stop
Recoils Gas-jet
Miniaturizedliquid chromatography
Samplepreparation
-particlemeasurement
Cyclic, 80 s
AIDA apparatus
248Cm(18O,5n)261Rf (T1/2 = 78 S)
248Cm: 610 g/cm2
18O6+: 300 pnA
at JAEA tandem acceleratorChemistry Lab.
Eluent bottles
Ta disk reservoir
Micro-columns
He gas heaterHalogen lamp
Sampling table
Air cylinder
Pulse motorsSignal out
8 vacuum chambers
600 mm2 PIPS detectors
Preamp.
He/KCl gas-jetAIDA (Automated Ion-exchangeseparation apparatus coupled with theDetection system for Alpha-spectroscopy)
Cyclic discontinuous column chromatographic separationAutomated detection of -particles
ARCA
Excitation function of 248Cm(18O, 5n)261Rf
Maximum production cross section : ~ 13 nb at 94-MeV 18OProduction rate : ~ 2 atoms per minute
10-1
100
101
102
85 90 95 100 105 110
PresentSilva et al.PSIGhiorso et al.
Cro
ss s
ectio
n /
nb
Elab
/ MeV
7 8 9 10 11 120
5
10
15
20
25
30
7.5 8.5 9.5 10.5 11.5
Cou
nts
per
20 k
eV
261 R
f +
257 N
o
214 A
t + 21
4mA
t
212m
Po
211m
Po
218m
Fr
215 A
t + 21
1mP
o
211m
Po
-Energy / MeV
94-MeV 18O (2.35 x 1016 p / 4.0 h)
261Rf
78 s
257No
26 s
253Fm
3.0 d
Fluoride complex formation
M4+ + nF- ⇄ MF4+nn- (M=Zr, Hf, and Rf)
Fluoride anion (F-) strongly coordinates with metal cations. Formation of strong ionic bonds is expectedElectrostatic interaction between M4+ and F- charge density, ionic radius, etc.
Fast reaction kinetics of the fluoride complex formation
Ion-exchange chromatographic behavior of Rf, Zr, and Hf in hydrofluoric acid (HF) solution
Anion-exchange behavior of Rf, Zr, and Hf in HF
Column size: 1.0 mm i.d. 3.5 mmColumn size: 1.6 mm i.d. 7.0 mm
4226 cycles of anion-exchange experiments 266 events form 261Rf and 257No, 25 correlations
0
20
40
60
80
100
120
261Rf (Cm/Gd) 169Hf (Cm/Gd)85Zr (Ge/Gd)169Hf (Ge/Gd)
100 101
Ads
orpt
ion
prob
abili
ty
[HF]ini / M
(a)
100 101 102
261Rf (Gd/Cm)169Hf (Gd/Cm) 85Zr (Ge/Gd)169Hf (Ge/Gd)89mZr (Y)167Hf (Eu)
0
20
40
60
80
100
120
[HF]ini / M
(b)
[HF]ini / M
(b)
Rn-MF4+n + nHF2- ⇄ nR-HF2 + MF4+n
n- (M=Rf, Hf and Zr), R: resin
Kd vs. [HF2-]
100
101
102
103
10-1 100
Rf
Zr
Hf
Kd /
mL
g-1
[HF2-] / M
slope = -3
[MF7]3- (M = Zr and Hf)
slope = -2
[RfF6]2- ?
HF ⇄ H+ + F-
HF + F- ⇄ HF2-
HF ⇄ H+ + F-
HF + F- ⇄ HF2-
log Kd = C - nlog[HF2-]
[R-HF2 ]n [MF4+n n–]
[Rn-MF4+n ] [HF2–]n
K =[M]r
[M]aq
[Rn-MF4+n ]
[MF4+n n–]
[R-HF2 ]n
[HF2–]n
= =Kd =
slope = charge state of the metal complex
Conclusion
Large difference in the fluoride complex formation of Rffluoride complex formation of Rf and the lighter homologues Zr and Hf Fluoride complex formation: Rf < Zr ≈ Hf
According to the HSAB (Hard and Soft Acids and Bases) concept, the fluoride anion is a hard anion and interacts stronger with (hard) small cations. Thus, a weaker fluoride complex formation of Rf as compared to those of Zr and Hf would be reasonable if the size of the Rf4+ ion is larger than those of Zr4+ and Hf4+ as predicted with relativistic molecular calculations.
Zr4+ : 0.072 nmHf4+ : 0.071 nmRf4+ : 0.079 nm (prediction)
AcknowledgementAcknowledgement
JAERIJAERI - M. Asai, M. Hirata, S. Ichikawa, T. Ichikawa, Y. Ishii, - M. Asai, M. Hirata, S. Ichikawa, T. Ichikawa, Y. Ishii,
I. Nishinaka, T. K. Sato, H. Tome, A. Toyoshima, K. Tsukada, and I. Nishinaka, T. K. Sato, H. Tome, A. Toyoshima, K. Tsukada, and
T. YaitaT. Yaita
RIKENRIKEN - H. Haba - H. Haba
Osaka UnivOsaka Univ.. - H. Hasegawa, Y. Kitamoto, K. Matsuo, D. Saika, - H. Hasegawa, Y. Kitamoto, K. Matsuo, D. Saika,
W. Sato, A. Shinohara, and Y. TaniW. Sato, A. Shinohara, and Y. Tani
Niigata UnivNiigata Univ.. - S. Goto, T. Hirai, H. Kudo, M. Ito, S. Ono, and J. Saito - S. Goto, T. Hirai, H. Kudo, M. Ito, S. Ono, and J. Saito
Tokyo Metropolitan UnivTokyo Metropolitan Univ.. - H. Nakahara and Y. Oura - H. Nakahara and Y. Oura
Univ. TsukubaUniv. Tsukuba - K. Akiyama and K. Sueki - K. Akiyama and K. Sueki
Kanazawa UnivKanazawa Univ.. - H. Kikunaga, N. Kinoshita, and A. Yokoyama - H. Kikunaga, N. Kinoshita, and A. Yokoyama
Univ. TokushimaUniv. Tokushima - M. Sakama - M. Sakama
GSIGSI - W. Brüchle, V. Pershina, and M. Schädel - W. Brüchle, V. Pershina, and M. Schädel
Univ. MainzUniv. Mainz - J. V. Kratz - J. V. Kratz
Kd vs. [NO3]- in HF/HNO3
Rn-MF4+n + nNO3- ⇄ nR-NO3 + MF4+n
n- : n = -2
100
101
102
103
104
105
10-2 10-1 100
Kd /
mL
g-1
[NO3-] / M
Rf: slope = -2 [RfF6]2-
Zr, Hf: slope = -2 [MF6]2- (M=Zr, Hf)
closed (on-line)open (off-line)
[F-] = 3 x 10-3 M
HF ⇄ H+ + F-
(HF + F- ⇄ HF2-)
HNO3 ⇄ H+ + NO3-
HF ⇄ H+ + F-
(HF + F- ⇄ HF2-)
HNO3 ⇄ H+ + NO3-
log Kd = C - nlog[NO3-]
Kd vs. [F-] in HF/HNO3
MF5- MF6
2- RfF5- RfF6
2-
HF2-
counter ion
3x10-3 M
101
102
103
104
10-6 10-5 10-4 10-3 10-2 10-1
Kd /
mL
g-1
[F-] / M
0.01 M HNO3
(AIX)
0.03 M HNO3
(AIX)
0.01 M HNO3
(AIX)
0.015 M HNO3
(AIX)
0.1 M HNO3
(AIX)
0.1 M HNO3
(CIX)
Rf (on-line)Zr (off-line)Hf (off-line)
Rf (on-line)Zr (off-line)Hf (off-line)
Formation of [MF6]2-: Zr Hf > Rf
Energy levels of the valence ns and (n-1)d electrons
-0.5
-0.4
-0.3
-0.2
-0.1
0
Orb
ital E
nerg
y /
a.u.
Ti Zr Hf Rf
nr nr nr nrrel rel rel rel
5s 6s 7s4s 4s1/2
5s1/2
6s1/2
7s1/2
3d 3d3/2
3d5/2
4d 4d3/2
4d5/2
5d
5d5/2
5d3/2
6d3/2
6d5/2
6d
rel: relativisticnr: non-relativistic
non-rel rel
distance(a.u.)
rad
ial
den
sity
r
R(r
)
J A E R I
0 2 4 0 2 4
0
1
-1
spin-orbit coupling
Rf 5fRf 6s
Rf 6d
Contraction of orbitals
Rf 6p
Radial wave functions of valence orbitals for Rf
18O Beam
248Cm Target on Be Backing
HAVAR Window2.0 mg/cm2
Gas-jet Outlet
Gas-jet Inlet(He/KCl)
Water CooledBeam Stop
He Cooling Gas
Recoils
248Cm(18O,5n)261Rf (78 s), 18O6+ beam: 300 pnA
248Cm target: 610 g/cm2
MANON: Measurement system for Alpha-particle and spontaneous fissioN events ON-line
Si PIN Photodiodes Catcher Foil120 mg/cm2, 20 mm i.d.
Wheel Rotation
Production of 261Rf
Production rates of transactinide nuclides used for chemistry study
Z Nuclide T1/2 (s) Reaction (nb) Production
rate*
104 261Rf 78 248Cm(18O,5n) 13 4 min-1
105 262Db 34 248Cm(19F,5n) 1.5 0.5 min-1
106 265Sg 7.4 248Cm(22Ne,5n) 0.24 5 h-1
107 267Bh 17 249Bk(22Ne,4n) 0.06 1 h-1
108 269Hs 14 248Cm(26Mg,5n) 0.006 3 d-1
* Assuming typical values of 0.8 mg/cm2 for the target thickness and beam intensities
of 3x1012 particles per second.
Atom-at-a-time-chemistryAtom-at-a-time-chemistry
Times
1
2
3
4
5
6
7
8
: :: :
“Classical”
“Single atom”
Phase 2Phase1
Activity 1 >> Activity 2
Phase 1 Phase 2
Probability 1 >> Probability 2
Anion-exchange procedure in HF with AIDAAnion-exchange procedure in HF with AIDA1. Collection of 261Rf and 169Hf for 125 s2. Dissolution with 240 L of 1.9 M - 13.9 M HF and feed onto the column at 740 L/min
AIX column: MCI GEL CA08Y resin (20 m)1.6 mm i.d. 7.0 mm (1.0 mm i.d. 3.5 mm)
3. 210 L of 4.0 M HCl at 1.0 mL/min
Fraction 1 (A1) Fraction 2 (A2)
Adsorption probability = 100 A2 / (A1 + A2)
169Hf : elution behavior and chemical yields (~ 60%)85Zr and 169Hf from Ge/Gd target
N
+
+
HF2-
HF2-
RfF62-
HF2-
R2-RfF6 + 2HF2- ⇔ 2R-HF2 + RfF6
2-
HF solutionAnion-exchange resin
RfF62-
r
N
HF2-
Anion-exchange between RfF62- and HF2
-
rrr
rrrrr
Adsorption on resin
exchanger
N
+
+
N
r
HF H+ + F-
HF + F- HF2-
HF H+ + F-
HF + F- HF2-
Anion-exchangein HF
Automated Ion exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA)
AIDAHe/KCl Jet in
Slider
Eluent inCollection site
Sample
5 cm
Magazine20 micro-columns, MCI GEL CA08Y, 22 m1.6 mmΦ x 7.0 mm or 1.0 mmΦ x 3.5 mm
Anion-exchange procedures for Rf andAnion-exchange procedures for Rf and the homologues, Zr and Hf in HFthe homologues, Zr and Hf in HF
4 M HCl200–210 μL Gas out
Magazine
1.9–13.9 M HF240–260 μL
α/γ-spectroscopy
1st fraction
2nd fraction
Front view Side view
Ta disk
Schädel et al. RCA 48(1989)171.
Actinide contraction: The radii of the actinide ions (An3+) are observed to decrease with increasing positive charge of the nucleus. This contraction is a consequence of the addition of successive electrons to an inner f electron shell, so that the imperfect screening of the increasing nuclear charge by the additional f electron results in a contraction of the outer or valence orbital.
Element Z Ionic radius () Remarks
Ti
Zr
22
40
0.605
0.72
Hf 72 0.71 Lanthanide contraction
Rf 104 0. 79
(prediction)
Actinide contraction
+ Relativistic effect
Ionic radii of the group-4 elements (M4+)
Assuming that the adsorption equilibrium of an ion MF4+n n– can be represented by the
equation,
Rn-MF4+n + nHF2– ⇔ nR-HF2 + MF4+n
n–
(where R represents the resin), one obtains the mass action constant
The distribution coefficient Kd is expressed as
Thus, the following equation is deduced
For tracer solutions, the following simplification will be assumed using the constant c
[R-HF2]n = c .
[R-HF2 ]n [MF4+n n–]
[Rn-MF4+n ] [HF2–]n
K =
[M]r
[M]aq
Kd =[Rn-MF4+n ]
[MF4+n n–]
= =1
K
[R-HF2 ]n
[HF2–]n
log Kd = log [R-HF2 ]n
K- nlog [HF2
–]
≈ c - nlog [HF2–].
.
.
Charge state n of an anion MF4+nn–
(M4+ = Rf, Zr and Hf)
Simultaneous production of Rf, Zr and HfSimultaneous production of Rf, Zr and Hf
248Cm target: 610 g/cm2
18O6+ beam: 300 pnA
18O Beam
248Cm Target on Be Backing
HAVAR Window2.0 mg/cm2
Gas-jet Outlet
Gas-jet Inlet(He/KCl)
Water CooledBeam Stop
He Cooling Gas
Recoils Rapid Chemical Separation Apparatus AIDA
Target recoil chamber + gas-jet transport systemTarget recoil chamber + gas-jet transport system
248248Cm(Cm(1818O,5O,5nn))261261Rf (78 s) + Gd(Rf (78 s) + Gd(1818O,O,xnxn))169169Hf (3.24 min)Hf (3.24 min)
natnatGe(Ge(1818O,O,5n5n))8585Zr (7.86 min) + Gd(Zr (7.86 min) + Gd(1818O,O,xnxn))169169Hf (3.24 min) Hf (3.24 min)
Chemical experiments on Rf should be conducted togetherwith the homologues under strictly identical conditions.
Anion-exchange behavior
of Rf, Zr and Hf in HCl 11
23 4
11 12
3 4 5 6 719 20 21 22 23 24 25
37 38 39 40 41 42 43
55 56 57 72 73 74 75
87 88 89 104 105 106 107
H
Li
Na Mg
Be
K Ca Sc Ti V Cr Mn
Rb
Cs Ba La
MoNbZrY
Ta W
Sr Tc
Hf Re
Db Sg BhFr Ra Ac Rf
Adsorption of Rf is similar to those of Zr and Hf.- typical behavior of the group-4 element
0
20
40
60
80
100
Hf (Cm/Gd)Rf (Cm/Gd) Zr (Ge/Gd)Hf (Ge/Gd)
3 5 7 9 11
Ads
orpt
ion
/ %
HCl concentration / M
Upper part of the chart of nuclides 118
117
116
115
114
113
112
Rg
Ds
Mt
Hs
Bh
Sg
Db
Rf
152 153 155 157 159 161 162 163 165 167 169 171 173 175
114 2860.29 s
Rf 26178 4.2 s s
Sg 2582.9 ms
Rf 2566.2 ms
Db 2570.8 1.5s s
Rf 25813 ms
Db 2584.4 s
Rf 2593.1 s
Db 2611.8 s
Db 26234 s
Db 26327 s
Sg 2603.6 ms
Hs 2662.3 ms
Rf 263~15 m
Rf 26020 ms
Rf 262 47 2.1 ms s
Db 2590.5 s
Db 2601.5 s
Db 26773 m
Db 26816 h
Sg 2590.48 s
Sg 2610.23 s
Sg 2626.9 ms
Sg 263 0.3 0.9 s s
Sg 2657.9 s
Sg 26621 s
Bh 26111.8 ms
Bh 262102 8.0 ms ms
Bh 2641.0 s
Bh 2662.47 s
Bh 26717 s
Bh 271 ?
Bh 2729.8 s
Hs 265 0.8 1.7 ms ms
Hs 26759 ms
Hs 26914 s
Hs 2702.4 s
Hs 27711 m
Hs 2640.26 ms
Mt 2661.7 ms
Mt 26842 ms
Mt 2759.7 ms
Mt 2760.72 s
Ds 2673.1μs
?
Ds 269170μs
Ds 270100 6 μs ms
Ds 2711.1 56ms ms
Ds 2730.15 ms
Ds 2819.6 s
Rg 2721.6 ms
Rg 279170 ms
Rg 2803.6 s
112 2770.6 ms
112 2836.1 s
112 28498 ms
112 28534 s
113 283100 ms
113 2840.48 s
114 2871.1 s
114 2880.63 s
114 2892.7 s
115 28732 ms
115 28887 ms
116 29015 ms
116 2916.3 ms
118 2941.8 ms
Rf 257 4.7 s
116 29353 ms
Ds 2790.29 s
112 2821.0 ms
Bh 2650.94 s
113 278344 s
Rg 2749.26 ms
Mt 2707.16 ms