Transcript Recent achievements in the search for superheavy elements

Trends in heavy ion sciences 24 May, 2008
Why experimenters like to come to Dubna: Scientific
success is always a good reason to organize a big party!
Trends in heavy ion sciences 24 May, 2008
Laboratory for Radiochemistry and Environmental Chemistry
How chemists have reached the island of spherical
superheavy elements
Heinz W. Gäggeler
Paul Scherrer Institut and
Bern University, Switzerland
 Chemistry of volatile 7p-elements = chemistry of
spherical SHE
 Recent studies with IVO: In-Situ volatilisation and Online detection (developed for first chemical study of
hassium but recently applied for element 112 and 114)
 Are relativistic effects influencing the chemical property
of element 114?
Trends in heavy ion sciences 24 May, 2008
island of
Superheavy
Elements
114
strait
of
instability
Number of protons
peak of U
peak of Pb
82
strait
of
radioactivity
sea of instability
50
peak of Sn
20
sea of instability
peak of Ca
20
82
126
Number of neutrons
G.N. Flerov, A.S. Ilyinov (1982)
184
Shell stabilisation
spherical
deformed
Courtesy: S. Hofmann
Trends in heavy ion research, 24 May 2008
Periodic
Periodic Table
Table of
of the
the Elements
1
18
1
2
H
2
13
14
15
16
17
He
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
11
12
13
14
15
16
17
18
Na Mg 3
4
5
6
7
8
9
10
11
12
Al
Si
P
S
Cl
Ar
19
20
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca Sc
Ti
V
Cr
Mn Fe
Co Ni
Cu Zn
Ga Ge As
Se
Br
Kr
37
38
39
40
41
42
43
45
47
48
49
50
51
52
53
54
Y
Zr
Nb Mo Tc
Ru Rh Pd
Ag
Cd
In
Sn
Sb Te
I
Xe
72
73
74
75
76
78
79
80
81
82
83
84
85
86
La
Hf
Ta
W
Re Os Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
89
104
105
106
107
Rf
Db
Sg Bh
115
115
116
116
116
69
70
Rb Sr
21
55
56
57
Cs
Ba
87
88
Fr
Ra Ac
44
77
46
108
Hs
114
112
109
110
111
Mt
Ds
Ds Rg
Rg
63
64
113
113
114
66
67
68
118
118
--
Lanthanides
58
Ce Pr
Nd Pm Sm Eu
Gd Tb
Dy
Ho Er
Tm Yb
Lu
Actinides
90
91
92
93
96
98
99
100
101
103
Th
Pa
U
Np Pu Am Cm Bk
Cf
Es
Fm Md No Lr
59
60
61
62
94
95
65
97
102
71
Mendelejev‘s first Periodic Table
from 1871
Basis for the discovery of several new elements!
Positioning of new elements
into the Periodic table
1
18
1
2
H
2
3
4
Li
Be
11
12
1993
-- 1997
≥ 2007
2001
2000
2007
2002
13
14
15
16
17
He
5
6
7
8
9
10
B
C
N
O
F
Ne
13
14
15
16
17
18
Na Mg 3
4
5
6
7
8
9
10
11
12
Al
Si
P
S
Cl
Ar
19
20
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca Sc
Ti
V
Cr
Mn Fe
Co Ni
Cu Zn
Ga Ge As
Se
Br
Kr
37
38
39
40
41
42
43
45
47
48
49
50
51
52
53
54
Rb Sr
Y
Zr
Nb Mo Tc
Ru Rh Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
55
56
57-71
72
73
74
75
76
78
79
80
81
82
83
84
85
86
Cs
Ba
La
Hf
Ta
W
Re Os Ir
Pt
Au
Hg Tl
Pb
Bi
Po
At
Rn
87
88
89-103
104
105
106
107
112
114
Fr
Ra Ac
Rf
Db Sg
115
116
21
44
77
108
--
Bh Hs
106
108
107
Sg Bh Hs
57
58
59
Lanthanides La Ce Pr
Actinides
60
46
61
62
109
110
111
112
Mt
Ds Rg
--
63
64
65
-114
113
-66
67
118
-68
69
70
71
Nd Pm Sm Eu
Gd Tb
Dy
Ho Er
Tm Yb
Lu
96
98
99
100
101
103
Cf
Es
Fm Md No Lr
89
90
91
92
93
94
95
97
Ac
Th
Pa
U
Np Pu Am Cm Bk
102
Reactions used and number of atoms found in the „first ever
chemical studies“ in the last decade
Bohrium (Z=107); Main experiment at PSI
249Bk(22Ne;4n)267Bh (T = 17 s); 6 atoms (R. Eichler et al., Nature, 407, 64 (2000))
1/2
Hassium (Z=108); Main experiment at GSI
248Cm(26Mg;5n)269Hs(T = 15 s); 7 atoms (C.E. Düllmann et al., Nature, 418, 860 (2002))
1/2
Element 112; Main experiment at FLNR/JINR
242Pu(48Ca,3n)287114 (T = 0.5 s)283112 (T = 4 s); 2 atoms (R. Eichler, Nature, 447,
1/2
1/2
72,2007); meanwhile 5 atoms in total (R. Eichler et al., Angew. Chem. Int. Ed., 47,1(2008))
Element 114: Main experiment at FLNR/JINR; ongoing. Currently evidence for 3 - 5 atoms
Trends in heavy ion research, 24 May 2008
Gas flow
Yield [%]
Temperature [°C]
Isothermal Chromatography: Sg,Bh
T50%
tRet. = T1/2
low Temperature [°C] high
Column length [cm]
Ta
Gas flow
Yield [%]
Temperature [°C]
Thermochromatography: Hs, Z=112; Z=114
Column length [cm]
high Temperature [°C] low
1
Elements with Z ≥ 112: filled 6d10 shell:
7p-element behaviour (volatile noble metals)
18
1
2
H
2
13
14
15
16
17
He
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
11
12
13
14
15
16
17
18
Na Mg 3
4
5
6
7
8
9
10
11
12
Al
Si
P
S
Cl
Ar
19
20
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca Sc
Ti
V
Cr
Mn Fe
Co Ni
Cu Zn
Ga Ge As
Se
Br
Kr
37
38
39
40
41
42
43
45
47
48
49
50
51
52
53
54
Y
Zr
Nb Mo Tc
Ru Rh Pd
Ag
Cd
In
Sn
Sb Te
I
Xe
72
73
74
75
76
78
79
80
81
82
83
84
85
86
La
Hf
Ta
W
Re Os Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
89
104
105
106
107
Rf
Db
Sg Bh
115
115
116
116
116
69
70
Rb Sr
21
55
56
57
Cs
Ba
87
88
Fr
Ra Ac
44
77
46
108
Hs
114
112
109
110
111
Mt
Ds
Ds Rg
Rg
63
64
113
113
114
66
67
68
118
118
--
Lanthanides
58
Ce Pr
Nd Pm Sm Eu
Gd Tb
Dy
Ho Er
Tm Yb
Lu
Actinides
90
91
92
93
96
98
99
100
101
103
Th
Pa
U
Np Pu Am Cm Bk
Cf
Es
Fm Md No Lr
59
60
61
62
94
95
65
97
102
71
How to experimentally determine a metallic
character of a volatile element at a single
atom level?
→ Determine interaction energy (adsorption
enthalpy) with noble metals (e.g. Au)
→ If metallic: strong interaction (adsorption
enthalpy) if non-metallic (noble gas like):
weak interaction
Adsorption of single atoms of mercury
and radon on a gold surface
50
500
45
450
Hads = -87 kJ/mol
219Rn
Hads = -27 kJ/mol
400
35
350
30
300
25
250
20
200
15
150
10
100
5
50
0
0
1
3
5
7
9
11
13
15
17 19
lenght [cm]
21
23
25
27
29
31
temperature [K]
yield [%]
40
192Hg
Adsorption of single atoms of mercury and radon
on a quartz surface
60
192Hg
Hads = -24.5 kJ/mol
219Rn
Hads = -20.5 kJ/mol
400
350
40
yield [%]
450
300
30
250
200
20
150
100
10
50
0
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
lenght [cm]
temperature [K]
50
500
Correlation between adsorption properties of single atoms
on gold and their macroscopic sublimation enthalpy
250
Po Pb
experimantal data
least square fit:
95% c.i.
Tl
Bi
-Hads(Au), kJ/mol
200
150
Hg
100
At
Xe
50
Rn
-Hads(Au) = (1.08±0.05)*Hsubl+(10.3±6.4), kJ/mol
Kr
0
0
50
100
150
200
250
Hsubl, kJ/mol
Trends in heavy ion science, 24 May 2008
Element 112
similar to Hg?
1
18
1
2
H
2
13
14
15
16
17
He
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
11
12
13
14
15
16
17
18
Na Mg 3
4
5
6
7
8
9
10
11
12
Al
Si
P
S
Cl
Ar
19
20
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca Sc
Ti
V
Cr
Mn Fe
Co Ni
Cu Zn
Ga Ge As
Se
Br
Kr
37
38
39
40
41
42
43
45
47
48
49
50
51
52
53
54
Y
Zr
Nb Mo Tc
Ru Rh Pd
Ag
Cd
In
Sn
Sb Te
I
Xe
72
73
74
75
76
78
79
80
81
82
83
84
85
86
La
Hf
Ta
W
Re Os Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
89
104
105
106
107
Rf
Db
Sg Bh
115
115
116
116
116
69
70
Rb Sr
21
55
56
57
Cs
Ba
87
88
Fr
Ra Ac
44
77
46
108
112
Hs
109
110
111
Mt
Ds
Ds Rg
Rg
63
64
114
113
113
114
66
67
68
118
118
--
Lanthanides
58
Ce Pr
Nd Pm Sm Eu
Gd Tb
Dy
Ho Er
Tm Yb
Lu
Actinides
90
91
92
93
96
98
99
100
101
103
Th
Pa
U
Np Pu Am Cm Bk
Cf
Es
Fm Md No Lr
59
60
61
62
94
95
65
97
102
71
Texas A&M, Nov. 2007
The element 112 experiment
(IVO [In-situ Volatilisation and On-line detection]
Technique)
Beam (48Ca; 233-239 MeV)
Window/
Target (242Pu:
 1.4 mg/cm2)
Recoil
chamber
Beam
stop
Teflon
capillary
SiO2-Filter
Ta metal
850°C
Quartz
inlay
Cryo On-line Detector (4p COLD)
(32 pairs PIN diodes, one side gold covered)
Hg
Quartz
column
112
Loop
Rn
Temperature gradient: 35°C to – 184 °C
T
Carrier gas
He/Ar (70/30)
l
Studies on element 112



242Pu(48Ca;3n)287114
(0.5 s) → 4s
283112
Reasons
a) High cross section of  5 pb ( 3-times higher than
via direct production with 238U as a target)
b) Residence time in collection chamber and transport
283112
capillary  2 s
4s
a 9.54 MeV
Rf
Ds261
279
4s
0.2 s
a 8.5 MeV
Trends in heavy ion science, 24 May 2008
Excitation functions
Cross sections / 3 MeV (relative units)
xn-channel cross sections
from 242,244Pu+48Ca reactions
50
10
3n
2n
3n
4n
5n
4n
5
1
2n
0.5
5n
0.1
25
30
35 40
55
50
45
Excitation energy (MeV)
Courtesy: Yu. Oganessian. “Heaviest Nuclei from 48Ca-induced Reactions” TAN-07, Davos, Sept. 23-27, 2007
Trends in heavy ion science, 24 May 2008
Laboratory for Radiochemistry and Environmental Chemistry
Result from the 48Ca + 242Pu experiment
Observed in Chemistry:
11.05.2006
2:40 (moscow time)
25.05.2006
8:37 (moscow time)
287114
287114
First independent confirmation of 283112 formation and
283112
283112
decay properties! (R. Eichler et al., Nature, 447, 72 (2007))
9.48 MeV
9.37 MeV
279Ds
279Ds
t: 0.592 s
SF
t: 0.536 s
SF
108+123 MeV
127+105 MeV
Three week bombardment with 3.1x1018 48Ca ions at 236 ± 3 MeV
Result from additional 48Ca + 242Pu experiments
in 2007
The chemistry experiment is not sensitive to the 4n channel (too
short-lived nuclides)
287114
287114
287114
283112
283112
283112
9.52 MeV
9.35 MeV
9.52 MeV
279Ds
279Ds
279Ds
t: 0.072 s
SF
t: 0.773 s
SF
t: 0.088 s
SF
112 + n.d MeV
85+12 MeV
94+51 MeV
Bombardment 21.3.- 17.4. 2007 with 3.1x1018 48Ca ions at 237± 3 MeV
The chemistry of element 112
50
50
a)
40
283
112
ice
gold
0
30
-50
185
20
219
Hg
Rn
10
-100
-150
0
-200
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Rel. yield / detector, %
50
gold
40
30
185
ice
219
Hg
20
283
0
-50
Rn
-100
112
10
-150
0
Temperature, °C
50
b)
-200
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
50
50
c)
ice
gold
40
0
30
-50
185
20
Hg
219
283
Rn
-100
112
10
-150
0
-200
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Detector #
Element 112 is similar to Hg, but slightly more volatile
Deduced adsorption enthalpy:
-52+20-4 kJ/mol (black solid line)
The chemistry of element 112
250
Po Pb
experimantal data
least square fit:
95% c.i.
Tl
Bi
-Hads(Au), kJ/mol
200
150
Hg
100
At
-52+20-4 kJ/mol 50
Xe
Rn
-Hads(Au) = (1.08±0.05)*Hsubl+(10.3±6.4), kJ/mol
Kr
0
0
50
100
150
200
250
Hsubl, kJ/mol
Hsubl=39+23-10 kJ/mol (68% c.i.)
Trends in heavy ion science, 24 May 2008
Trend of sublimation enthalpy within group 12
160
Zn
140
Hsubl, kJ/mol
120
Cd
100
Hg
80
60
40
112
20
0
0
20
40
60
80
100
120
Z
Trends in heavy ion science, 24 May 2008
What‘s next?
• Search for relativistic effects in the chemistry
of element 114 (group 14 with [Rn]7s26d107p2)
• Relativistic effect: influence of increasing
Coulomb attraction between atomic electrons
and nucleus
Trends in heavy ion science, 24 May 2008
Group 14:
6d107s27p2
Prediction by Pitzer (1975)
Is element 114 a noble gas due to a strong
spin-orbit splitting of the 7p orbitals?
from: V. Pershina et al., J. Chem. Phys., 127, 134310 (2007)
Studies on element 114

Reaction: 242Pu(48Ca;3n)287114 (T1/2
=0.5s) (FLNR; spring 2007)
287114
1 atom on Au at – 80 °C
a 10.0 MeV
3.1x1018 48Ca ions at 237± 3 MeV
283112
10.9 s
a 9.54 MeV
Rf
Ds261
279
4s
0.24s
a 8.5 MeV
unpublished
Trends in heavy ion science, 24 May 2008
Studies on element 114

Reaction:
=0.8s)
244Pu(48Ca;4n)288114
(T1/2
2 atoms on Au at –10 °C & -84 °C
Beam dose 4x1018
Energy within targets:
243 – 231 MeV
(~ 1.4 mg/cm2)
284261
Rf
112
4s
0.11 s
a 8.5 MeV
unpublished
288114
288114
a 9.95 MeV
a 9.81 MeV
284112
0.11 s
Trends in heavy ion science, 24 May 2008
Current experiment
lasting until 8 June 2008
at FLNR:
48Ca + 244Pu
to produce
0.8 s 288114 (4n-channel)
2.7 s 289114 (3n-channel)
Chemistry behind
the Dubna gasfilled separator
Pro & Contra
• Pro:
- Extremely clean a- spectra (no background)
- no sf-contamination by sputtered target
• Contra:
- Lower efficiency
- Smaller energy range in the thin target
Studies on element 114

289114
Reaction: 244Pu(48Ca;3n)289114
(T1/2 =2.7s) (FLNR; ongoing 2008) Not detected
10
Det 18 t+b 1 week 1x10
18
8
1 atom on Au at – 97 °C
285112
6
#/20 keV
4x1018 48Ca ions at E* = 38 – 42 MeV
a 9.12 MeV
4
281261
Rf
2 Ds
4s
3.3s
a 8.5 MeV
SF
0 106+50
5
6
7
8
9
E, MeV
unpublished
Trends in heavy ion science, 24 May 2008
50
gold
ice
Rel. yield / detector, %
8
287
114
6
-50
Hads =-35 kJ/mol
Au
4
-100
2
-150
0
-200
10
gold
50
ice
8
0
288
114
6
H
-50
Au
ads
4
Pu-244
0
=-35 kJ/mol
-100
2
-150
0
-200
2
4
6
8
10
12
14
16
18
20
Detector #
Decay during transport?
unpublished
22
24
26
28
30
32
Temperature, °C
Pu-24210
250
Po Pb
experimantal data
least square fit:
95% c.i.
Tl
Bi
-Hads(Au), kJ/mol
200
150
Hg
100
E114
At
Xe
50
Rn
-Hads(Au) = (1.08±0.05)*Hsubl+(10.3±6.4), kJ/mol
Kr
0
0
50
100
150
Hsubl, kJ/mol
200
250
Result from the chemistry experiment with
element 114
→ Element 114 exhibits a very weak adsorption
on Au, pointing to van der Waals interaction
(similar to a noble gas).
Conclusion




Chemical research on heaviest elements has
been much boosted by the recent discoveries of
many new nuclides up to Z=118 at FLNR
Chemical studies at the few atom level have
been sucessfully conducted up to Z = 112
Elements Bh, Hs & 112 (as well as Rf, Db, Sg)
behave in gas phase studies as expected from
extrapolations within the groups of the periodic
table
Ongoing studies point to an element 114
behaviour unlike that of eka-Pb, but rather
similar to a noble gas.
Trends in heavy ion science, 24 May 2008
Many thanks




To Yuri Oganessian for his constant
support and very active engagement
in the experiments
To Sergei Dmitriev and his team for
the Dubna chemists
To Georgi Gulbekian and his team for
the excellent 48Ca beams
To Robert Eichler and his team from
the PSI/Univ. Bern collaboration
Trends in heavy ion science, 24 May 2008
Raw data from few-hour measurement with pre-separation
(GNS) (left) and without (right)
219Rn
215Po
211At
214Po
212Po