Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 205-210, 2005

Production and Chemistry of Transactinide Elements
Y. Nagame*
Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan
Received: July 31, 2005; In Final Form: September 30, 2005
Recent progress in production and chemistry of the transactinide elements, element 107 bohrium (Bh) and element
104 rutherfordium (Rf), is reviewed. First information on chemical properties of Bh was obtained in gas chromatographic experiments on an atom-at-a-time basis. Chemical separation and characterization of 6 atoms of267
Bh produced in the bombardment of a 249Bk target with 22Ne beams are outlined. Aqueous chemistry of Rf
being performed at JAERI (Japan Atomic Energy Research Institute) is briefly summarized. On-line anionexchange experiments in acidic solutions on 261Rf produced in the 248Cm(18O,5n) reaction were conducted with arapid ion-exchange separation apparatus. Characteristic anion-exchange behavior of Rf is discussed.

1. Introduction
According to the actinide concept,1 the 5f electron series ends
with element 103, lawrencium (Lr), and a new 6d electron transition series is predicted to begin with element 104, rutherfordium (Rf). The elements with atomic numbers Z ≥ 104 are called
transactinide elements or recently called superheavy elements.2
The currently known transactinide elements, elements 104
through 112, are placed in the periodic table under their lighter
homologues in the 5d electron series, Hf to Hg. Elements from
113 to 118 except for 117 synthesized by Oganessian et al.3, 4
would be in the successive 7p electron series (see Figure 1).
Studies of chemical properties of the transactinide elements
offer unique opportunities to obtain information about trends inthe periodic table of the elements at the limits of nuclear stability and to assess the magnitude of the influence of relativistic
effects on chemical properties. From calculations of electron
configurations of heavier elements, it is predicted that suddenchanges in the structure of electron shells may appear due torelativistic effects which originate from the increasingly strong
Coulomb field of a highly charged atomic nucleus.5 Therefore,
it is expected that heavier elements show a drastic rearrangement of electrons in their atomic ground states, and as electron
configurations are responsible for 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 consequently predicted.2, 6−8 It would
be no longer possible to deduce detailed chemical properties of
the transactinide elements simply from the position of the periodic table.
1

18
2

1

H

2

13

14

15

16

17

He

3

4

5

6

7

8

9

10

O

F

Ne

Li

Be

B

C

N

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

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

K

Cr

Mn

Ni

Cu

Zn

Ga

Ge

As

Ca

Sc

Se

Br

37

38

39

40

41

42

43

44

45

46

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

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

W

Re

Os

At

Cs

Ba

Ti

V

Fe

Co

Kr

La

Hf

Hg

Tl

Pb

Bi

Po

87

88

89

104

105

106

107

108

109

110

111

112

113

114

115

116

118

Fr

Ra

Ac

Rf

Db

Sg

Bh

Hs

Mt

Ds

Rg

112 113 114 115 116

118

Ta

Ir

Pt

Au

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

La

Ce

Pr

Nd

Pm

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

Ac

Th

Pa

U

Np

Pu

Am

Cm

Bk

Cf

Es

Fm

Md

No

Lr

Rn

Figure 1. Periodic table of the elements.
*Corresponding author. E-mail: nagame.yuichiro@jaea.go.jp.
FAX: +81-29-282-5927.

Chemical experiments with the transactinide elements are
generally divided into the following 4 basic steps; i) synthesisof transactinide nuclides, ii) rapid transport of the synthesized
nuclides to chemical separation apparatuses, iii) fast chemical
isolation of a desired nuclide and preparation of a sample suitable for nuclear spectroscopy, and iv) detection of nuclides
through their characteristic decay properties. Due to short halflives and low production rates of the transactinide nuclides,
each atom produced decays before a new atom is synthesized.
This means that any chemistry to be performed must be doneon an “atom-at-a-time” basis.2, 9, 10 Thus, rapid and very efficientradiochemical procedures must be devised. Recent comprehensive reviews on the chemistry of the transactinide elements arefound in References 2, 9, and 10.
The first successful chemical isolation and identification of
Bh was accomplished in an experiment at the Philips cyclotronof PSI (Paul Sherrer Institute) by Eichler et al.11 The resultclearly indicated that the volatile bohrium oxychloride complex
behaved like a typical member of group 7 of the periodic tableof the elements. From recent systematic studies of the anionexchange behavior of Rf, it was found that Rf is a member ofthe group 4 elements,12 although unexpected chemical behaviorof Rf was observed in the fluoride complex formation.13
In this paper, chemical studies on gas chromatographic
behavior of Bh at PSI and aqueous chemistry of Rf at JAERI
are outlined.
2. Production of Transactinide Elements
Longer-lived transactinide nuclides required in chemical
experiments exit in the neutron-rich region of the chart ofnuclides and they are produced in so-called hot fusion reactions of such beams as 18O, 19F, 22Ne, and 26Mg with actinides
targets of 244Pu, 248Cm, 249Bk, and so on. The produced transactinide nuclides must be identified by measurement of theirdecay or by that of their known daughter nuclei with unambiguous detection techniques.
A schematic representation of a typical experimental set-up
for the production of transactinide nuclides is shown in Figure
2 where the target and recoil chamber for the production of261
Rf at JAERI are depicted. A 248Cm target of 610 µg/cm 2
thickness prepared by electrodeposition of Cm(NO3)3 from isopropyl alcohol onto 2.4 mg/cm2 thick beryllium backing foil isbombarded by 18O beams delivered from the JAERI tandem
accelerator. The 18 O 6 + beam passes through 2.0-mg/cm 2
HAVAR entrance window foil, 0.09 mg/cm 2 He cooling gas© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

206 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

NagameHe cooling gas
248Cm target on Be backing

gas-jet outlet
18O beamwater cooledbeam stop

HAVAR
window foil
2.0 mg/cm2

recoils

gas-jet inlet(He/KCl aerosols)

chemistrylaboratory

Figure 2. Schematic diagram of a target recoil chamber arrangementwith a gas-jet system.

and the beryllium target backing, and it finally enters the 248Cm
target material. The reaction products recoiling out of the target are thermalized in a volume of He gas (≈ 1 bar) which isloaded with potassium chloride (KCl) aerosols generated bysublimation from the surface of KCl powder at 640 ˚C. The
products attached to the aerosols are swept out of the recoilchamber with the He gas flow (2.0 L/min) and are transported
through a Teflon-capillary (length 20 m, inner diameter 2.0mm) by a He/KCl gas-jet system to a chemistry laboratory.
The reactions and the expected production rates of the transactinide nuclides used for chemical studies are summarized inTable 1. Assuming the typical values of 800 µg/cm 2 for thetarget thickness and the beam intensity of 3 × 1012 s−1, one cananticipate the production rates, for example, to be 4 atoms per
minute for Rf and a 1 atom per hour for Bh.
3. Gas-phase Chemistry of Element 107, Bohrium (Bh)Figure 3 shows the schematic of the experiment for the gasphase chemistry of Bh.11 A target of 670 µg/cm2 249Bk covered
with a layer of 159Tb (100 µg/cm2) was bombarded for about 4
weeks with 22Ne beams at a beam energy of 119 MeV to produce 267Bh in the reaction 249Bk(22Ne,4n). Reaction products
recoiling from the target were adsorbed onto the surface of carbon particles in He gas and were then continuously transportedwith the gas-jet system to the chemistry apparatus OLGA III(On-Line Gas chromatography Apparatus).20 The aerosol particles were collected on quartz wool inside the reaction ovenkept at 1000 ˚C. A mixture of HCl and O2 as reactive gas wasintroduced to form volatile oxychlorides. The chromatographic
separation took place downstream in the isothermal temperature section of the quartz column (length 1.5 m, inner diameter
1.5 mm). The retention times of compounds in the column
depend mainly on their adsorption interaction with the surfaceof the column at the isothermal temperature and on the carriergas velocity. Thus, volatile molecules with a nuclear lifetime
longer than the retention time passed through the column, andwere subsequently attached to CsCl aerosol particles in Ar gas
and transported to the detection system ROMA (ROtating wheel
Multidetector Analyzer). The CsCl particles deposited in vacuum on thin foils mounted on the circumference of a stepwise

Figure 3. Schematic view of the Bh gas-chromatographic experiment. Courtesy of H. W. Gäggeler.
Tisothermal :75 ℃

Beam dose: 1.00 × 1018

150 ℃

180 ℃

1.00 × 1018

1.02 × 1018

Element

107

105

no decaychainsdetected

267Bh

8.81 MeV 8.85 MeV
34.4 s24.5 s

263Db

82 MeV

263Db

263Db

SF
21.1 s

103

267Bh

SF
98.9 s

46 MeV

267Bh

267Bh

267Bh

267Bh

8.72 MeV 8.84 MeV 8.91 MeV 8.81 MeV
26.7 s10.5 s18.4 s
2.9 s
263Db

263Db

263Db

8.40 MeV 8.35 MeV 8.37 MeV
0.8 s
73.4 s29.9 s259Lr

SF
16.3 s101 + 86 MeV

8.41 MeV
14.6 sFigure 4. Decay chains attributed to the decay of 267 Bh. The
observed α-particle and spontaneous fission decay energies and thelifetimes are given. Adapted from Reference 11.

rotating wheel. Every 10 s the collected samples were successively moved between a series of 12 pairs of PIPS (passivatedion-implanted planar silicon) detectors to measure the energy of
α-particles and spontaneous fission decay. Measurements were
performed at three different isothermal temperatures. Rhenium186 was simultaneously produced in the reaction 159Tb(22Ne,4n),
and was served as a yield monitor for the chemical separation
process. The overall yield, including transportation of the products with the gas-jet system, chemical yields, and sample preparation in the detection system, was on the average about 16% for
186
Re.11 The yield of 186Re was measured with an HPGe γ-ray
detector.
The nuclide 267Bh decays by α-particle emission to 263Db, an
isotope of element 105, which decays either by spontaneous fission or α-particle emission to 259Lr. About 180,000 samples
were measured throughout the experiment. As shown in Figure
4, four genetically linked decay chains attributed to the decay of

TABLE 1: Typical Nuclides Used in Chemical Studies of the Transactinide Elements
Atomic number
104
105
105
106
107
108
112

Nuclide
261

Rf
Db
262
Db
265
Sg
267
Bh
269
Hs
283
112
262

Half-life
78 s
34 s
34 s
7.4 s
17 s
14 s
5.1 min

Nuclear reaction
248

Cm(18O,5n)
Cm(19F,5n)
249
Bk(18O,5n)
248
Cm(22Ne,5n)249
Bk(22Ne,4n)
248
Cm(26Mg,5n)
238
U(48Ca,3n)
248

Production
cross section

Production rate*

Reference

13 nb
1.3 nb6 nb
0.24 nb
60 pb
6 pb
3 pb

4 min−1
0.5 min−1
2 min−1
5 h−1
1 h−1
3 d−1
1.5 d−1

14
14
15
16
17
18
19

*Assuming typical values of 800 µg/cm2 target thickness and 3 × 1012 s−1 beam particles. Partly adapted from Reference 10.

J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 207

Production and Chemistry of Transactinide Elements

He/KCl gas-jet

180
signal out

Relative yield /

160
140

100

pulse motors

169ReO Cl
3

120
108TcO Cl
3

PIPS detectors

80

preamp.

60
40

267BhO Cl
320

air cylinder
eluent bottles

0
-20

0

20

40

60

80

100

120

140

160

180

200

220

Tisothermal /ºC

Figure 5. Isothermal gas chromatographic behavior of the oxychloride compounds of Bh, Tc, and Re. The solid lines indicate the resultsof simulations with the microscopic model with the adsorption enthalpies given in the text. The dashed lines represent the calculated relative yield concerning the 68% confidence interval of the standard
adsorption enthalpy of BhO3Cl from –66 to –88 kJ/mol. Adaptedfrom Reference 11.
267

Bh were detected at an isothermal temperature of 180 ˚C,while at 150 ˚C, 2 decay chains were observed and no decay
chains were registered at 75 ˚C. A total of 6 atoms were detectedduring the experiment.11
Figure 5 shows the isothermal gas chromatographic behaviorof Bh oxychloride, presumably BhO3Cl, together with that of
the group 7 metal oxychlorides in quartz columns. The data for
Tc were obtained using a 252Cf spontaneous fission source in a
separate experiment.21 The relative yields of BhO3Cl after separation with the OLGA device are plotted as a function of isothermal temperatures and are compared with those of TcO3Cl
and ReO3Cl. The relative yield of BhO3Cl observed at 180 ˚C
was normalized to 100%. Although no 267BhO3Cl was observed
at 75 ˚C, 169ReO3Cl still passed the isothermal part of the column with about 80% of relative yield. From the gas adsorption
chromatographic behavior of those molecules, the following
enthalpies of adsorption on the column surface were deduced:–∆Ha0 (TcO3Cl) = 51 ± 3 kJ/mol, –∆Ha0 (ReO3Cl) = 61 ± 3 kJ/mol, and –∆Ha0 (BhO3Cl) = 75+6
−9 kJ/mol (68% confidence interval).11 The result clearly indicates that the sequence in volatility
is TcO3Cl > ReO3Cl > BhO3Cl. It is interesting to note that thissequence is consistent with predictions from relativistic densityfunctional calculations for group 7 oxychlorides22 and also fromclassical extrapolations of periodic trends.11 This means thatthe volatile BhO3Cl behaves like a typical member of group 7of the periodic table.11
4. Aqueous Chemistry of Element 104, Rutherfordium (Rf)
Ruthefordium-261 (T1/2 = 78 s) was produced at the JAERI
tandem accelerator. The mixed target of 248Cm (610 µg/cm2 inthickness) and Gd (39.3%-enriched 152Gd of 36 µg/cm2 in thickness) prepared by electrodeposition onto 2.4-mg/cm2 beryllium
foil was used for simultaneous production of 261Rf and 3.24-min
169
Hf via the 248Cm(18O,5n) and Gd(18O,xn) reactions, respectively. Hafnium-169 was served as a monitor of the on-line
chemistry experiment. The reaction products recoiling out of
the target were transported through a Teflon-capillary to thechemistry laboratory by the He/KCl gas-jet system as mentioned in Section 2. To perform rapid and cyclic anion-exchange
experiments with Rf, we employed an apparatus AIDA (Automated Ion-exchange separation apparatus coupled with the
Detection system for Alpha-spectroscopy)12, 23 that consisted ofa modified ARCA (Automated Rapid Chemistry Apparatus),24
which was a miniaturized computer controlled liquid chromatography system, and an automated on-line α-particle detection
system. AIDA enables us to perform cyclic discontinuous column chromatographic separation of short-lived nuclides in

micro-columns
halogen lamp
sampling tableHe gas heater
Ta disk reservoir

Figure 6. Schematic drawing of AIDA (Automated Ion-exchange
separation apparatus coupled with the Detection system for Alpha
spectroscopy). Adapted from Reference 23.

aqueous solutions and automated detection of α-particles
within a typical cycle of 1– 2 min. A schematic drawing ofAIDA is given in Figure 6. There are two column magazines,
each containing 20 micro columns. On-line anion-exchange
experiments on Rf together with the group 4 elements Zr and
Hf in acidic solutions, HCl, HNO3, and HF, were conductedwith AIDA. The adsorption behavior of Rf as a function of theacid concentration was systematically studied.12,13 Quite
recently, an elution curve of Rf has been obtained for the firsttime in anion-exchange chromatography on an atom-at-a-timebasis.25
In the following, the experimental procedures and the resulton the anion-exchange behavior of Rf in HCl solution are summarized. The reaction products continuously transported
through the He/KCl gas-jet system deposited on a collection
site of AIDA. After collection for 125 s, the site was mechanically moved on the top of one of the micro columns, where theproducts were dissolved with 170 µL of hot (≈ 80 °C) 11.5 M
HCl and then fed onto the chromatographic column (length
7mm, inner diameter 1.6 mm) filled with an anion-exchange
resin MCl GEL CA08Y (particle size of about 20 µm) at a flowrate of 1.0 mL/min. The products were eluted with 290 µL of
4.0 – 9.5 M HCl at a flow rate of 1.1 mL/min. The effluent wascollected on a Ta disk as fraction 1 and then evaporated to dryness using hot He gas and a halogen heat lamp for α-particle
measurement. The remaining products in the column were
eluted with 250 µL of 4.0 M HCl at a flow rate of 1.1 mL/min.
The effluent was collected on another Ta disk and evaporated
to dryness as fraction 2. The pair of disks was automaticallytransported to the α-spectroscopy station equipped with PIPS
detectors. After the α-particle measurement, γ-radiation of169
Hf was monitored with Ge detectors to determine the elution
behavior of Hf and its chemical yield. Each separation was
accomplished within 20 s and the α-particle measurement was
initiated within 80 s after the collection of products at the
AIDA collection site. The chemical yield of Hf, including collection and dissolution of the aerosols at the AIDA collection
site, was approximately 60%.12
From 1893 cycles of the anion-exchange experiments, a totalof 186 α events from 261Rf and its daughter 257No were registered, including 35 α-α correlation events.12 Figure 7 shows
the adsorption behavior of Rf, Zr, and Hf as a function of HClconcentration. We measured the adsorption probability of Zr
and Hf that were produced in the reactions Ge(18O,xn) andGd(18O,xn), respectively, under strictly identical conditions as
those with Rf and Hf.15 The ordinate shows the adsorption
probabilities of these elements, 100A2 /(A1+A2), where A1 and A2
are the eluted radioactivities observed in fractions 1 and 2,
respectively. The adsorption behavior of Rf is quite similar tothat of group 4 elements Zr and Hf. The adsorption of these208 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Nagame
10 3

Rf
Hf
Zr

100
80

Kd / mL g-1

Adsorption probability /%

120

60

10 1

Rf

Hf

40

Zr

20
0

10 0

3

4

5

6

7

8

9

10

11

12

HCl concentration / M
Figure 7. Adsorption probability of Rf, Zr, and Hf on the anionexchange resin CA08Y as a function of HCl concentration. Adaptedfrom Reference 12.
120

Adsorption probability /%

10 2

100
80
60
40

Rf
Hf
Zr

20
0

10 0

[HF] ini / M

10 1

Figure 8. Adsorption behavior of Rf, Zr, and Hf on the anionexchange resin CA08Y as a function of the initial concentration of
HF, [HF] ini. Adapted from Reference 13.

elements rapidly increases with increasing HCl concentration
higher than 7 M: typical anion-exchange behavior of group 4elements. This means that anionic chloride complexes of tetravalent Rf, Zr, and Hf are formed above 7 M concentration of
HCl.12
Similar behavior of Rf was also probed with the anionexchange experiment in 8 M HNO3. From 217 experiments, a
total of 20 α events from 261Rf and 257No were observed, including 5 time-correlated α pairs. It was found that Rf was eluted
from the column with 8 M HNO3 as expected for a typicalgroup 4 element.12 The above results definitely confirm that Rf
is an element of group 4.
Unexpected anionic-exchange behavior of Rf in HF solution
was observed. The experimental procedures with AIDA arebasically the same as those described above and the details are
given in Reference 13. From 4226 cycles of the anion-exchange
experiments, a total of 266 α events from 261Rf and its daughter
257
No were registered, including 25 time-correlated α pairs of261
Rf and 257No. Figure 8 shows a variation of the adsorption
probability of Rf, Zr, and Hf as a function of the initial concentration of HF, [HF]ini.13 Adsorption behavior of Zr was obtained
from the experiment using the Ge and Gd mixed target.13 The
adsorption of Zr is fairly equal to that of Hf over a wide rangeof HF concentrations and steeply decreases with [HF] ini, while

10-1[HF2 ] / M

100

Figure 9. Distribution coefficients (Kd) for Rf, Zr, and Hf on theanion-exchange resin CA08Y as a function of the concentration of
HF2−. Adapted from References 13 and 23.

that of Rf decreases at much lower [HF] ini. The lower adsorption of Rf indicates that the fluoride complexation of Rf is
weaker than those of Zr and Hf.
The dissociation of HF is expressed as,26→ HF
H+ + F − ←(1)→ HF − .
HF + F − ←2(2)In terms of the dissociation constants K1 = 935 M−1 for Equation(1) and K2 = 3.12 M−1 for Equation (2), above 1 M [HF] ini, theconcentration of anionic HF2− is more than one order of magnitude higher than that of free F−. The Kd values for Rf, Zr, and
Hf are plotted in Figure 9 as a function of the concentration of
HF 2 −, [HF 2 − ]. The Kd values for Rf were deduced from theadsorption probability in Figure 8 by assuming that the reaction rates in the fluoride complexation and the anion-exchange
process of Rf are as fast as those of the homologues Zr and Hf
as described in Reference 13. The Kd values for Zr and Hf werefrom the on-line column chromatographic experiments with
AIDA. A decrease of Kd values for these elements with [HF2−]
is explained as the displacement of the metal complex from thebinding sites of the resin with the counter ion HF2− as,→ n⋅R-HF + MF n−
Rn -MF4+n + n⋅HF2− ←24+n(M = Rf, Zr, and Hf),(3)

where R denotes the resin. As shown in Figure 9, Kd values ofthese elements decrease linearly with increasing [HF 2−] in thelog Kd vs. log [HF2−] plot. It should be noted that the slopes forZr and Hf are clearly –3 (dashed line), while that for Rf is –2(solid line). This means that Rf is likely to be present as ahexaf luoro complex, [Rf F 6 ] 2− similar to the well known[ZrF6] 2− and [HfF6] 2− at lower [HF] ini, while Zr and Hf arelikely to be present in the form of heptafluoro complexes,[ZrF 7] 3− and [HfF 7] 3− as suggested in References 27 and 28.
Activity coefficients of the chemical species involved are notavailable for higher concentration of HF, and the definite identification of the anionic fluoride complexes is still an open
question.
Relativistic density-functional calculations of the electronic
structures of hexafluoro complexes ([MF6] 2−, M=Rf, Zr andHf) have been performed to evaluate the stability of the complexes. The results of calculations that the sequence in theoverlap population between the valence d orbitals of M4+ andthe valence orbitals of F− is Zr ≈ Hf > Rf suggest that the Rf
complex is less stable than those of Zr and Hf in the [MF6] 2−
structure.29 Although the calculations qualitatively agree withthe experimental results, further theoretical approaches areProduction and Chemistry of Transactinide Elements

needed to quantitatively understand the present interesting
results.
5. Summary
Chemical studies of Bh and Rf on an atom-at-a-time basis
gave the following outcomes. Bohrium behaves like a typicalmember of group 7 of the periodic table and forms a volatile
oxychloride, presumably BhO3Cl, which is less volatile thanthose of the lighter homologues Tc and Re. The adsorption
behavior of Rf in anion-exchange chromatography is quite
similar to that of Zr and Hf in HNO3 and HCl solutions, clearly
confirming that Rf is an element of group 4. On the other
hand, a large difference was observed in the adsorption behavior of Rf on the anion-exchange resin in HF solution, i.e., thefluoride complexation of Rf is much weaker than those of thehomologues.
From artistic chemical studies of the transactinide elements
performed so far including the results described here, one canplace the elements 104 through 108 in their respective group of
the periodic table, i.e., Rf, Db, Sg, Bh, and Hs in group 4, 5, 6,
7, and 8, respectively.2, 7, 30 However, as observed in the fluoride complexation of Rf, unexpected chemical behavior partly
caused by relativistic effects would appear in chemical properties of the transactinide elements. To enhance the understanding on chemical properties of the transactinide elements, more
systematic experiments as well as quantitative theoretical calculations are required.
Acknowledgment. The author would like to thank his groupmembers in JAERI and all colleagues from RIKEN, Osaka,
Niigata, Kanazawa, Tokyo, Tsukuba, Shizuoka, Tokushima,
Darmstadt, and Mainz in the Rf experiment at JAERI. The
chemical studies on Rf are supported in part by the JAERIUniversity Collaboration Research Program and by the
Program on the Scientific Cooperation between JAERI and
GSI in Research and Development in the Field of Ion Beam
Application. He is grateful to H. W. Gäggeler for providing
him valuable information on the chemical studies of Bh.
References(1) G. T. Seaborg, Chem. Eng. News 23, 2190 (1945).
(2) The Chemistry of Superheavy Elements, ed. M. Schädel,Kluwer Academic Publishers, Dordrecht, 2003.
(3) Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh.
Abdullin, A. N. Polyakov, I. V. Shirokovsky, Yu. S.
Tsyganov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal,
A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov,
A. A. Voinov, G. V. Buklanov, K. Subotic, V. I. Zagrebaev,
M. G. Itkis, J. B. Patin, K. J. Moody, J. F. Wild, M. A.
Stoyer, N. J. Stoyer, D. A. Shaughnessy, J. M. Kenneally,
and R. W. Lougheed, Nucl. Phys. A734, 109 (2004).
(4) Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh.
Abdullin, A. N. Polyakov, I. V. Shirokovsky, Yu. S.
Tsyganov, G. G. Gulbekian, S. L. Bogomolov, A. N.
Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, A. A.
Voinov, G. V. Buklanov, K. Subotic, V. I. Zagrebaev, M. G.
Itkis, J. B. Patin, K. J. Moody, J. F. Wild, M. A. Stoyer, N.
J. Stoyer, D. A. Shaughnessy, J. M. Kenneally, and R. W.
Lougheed, Phys. Rev. C 69, 021601 (2004).
(5) B. Fricke and W. Greiner, Phys. Lett. 30B, 317 (1969).
(6) P. Pyykkö, Chem. Rev. 88, 563 (1988).
(7) V. Pershina, Chem. Rev. 96, 1977 (1996).
(8) P. Schwerdtfeger and M. Seth, Encyclopedia of Computational Chemistry, Vol. 4, eds. P. von R. Schleyer et al.,Wily, New York, 1998, p. 2480.
(9) J. V. Kratz, Chemistry of Transactinides. In: Handbook of
Nuclear Chemistry, Vol. 2, Elements and Isotopes, eds. A.

J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 209
Vértes, S. Nagy, Z. Klencsár, Kluwer Academic Publishers,
Dordrecht, 2003, p. 323.
(10) M. Schädel, J. Nucl. Radiochem. Sci. 3, 113 (2002).
(11) R. Eichler, W. Brüchle, R. Dressler, Ch. E. Düllmann, B.
Eichler, H. W. Gäggeler, K. E. Gregorich, D. C. Hoffman,
S. Hübener, D. T. Jost, U. W. Kirbach, C. A. Laue, V. M.
Lavanchy, H. Nitsche, J. B. Patin, D. Pluguet, M. Schädel,D. A. Shaughnessy, D. A. Strellis, S. Taut, L. Tobler, Y. S.
Tsyganov, A. Türler, A. Vahle, P. A. Wilk, and A. B.
Yakushev, Nature 407, 63 (2000).
(12) H. Haba, K. Tsukada, M. Asai, S. Goto, A. Toyoshima, I.
Nishinaka, K. Akiyama, M. Hirata, S. Ichikawa, Y. Nagame,Y. Shoji, M. Shigekawa, T. Koike, M. Iwasaki, A. Shinohara,
T. Kaneko, T. Maruyama, S. Ono, H. Kudo, Y. Oura, K.
Sueki, H. Nakahara, M. Sakama, A. Yokoyama, J. V. Kratz,
M. Schädel, and W. Brüchle, J. Nucl. Radiochem. Sci. 3,
143 (2002).
(13) H. Haba, K. Tsukada, M. Asai, A. Toyoshima, K. Akiyama,
I. Nishinaka, M. Hirata, T. Yaita, S. Ichikawa, Y. Nagame, K.
Yasuda, Y. Miyamoto, T. Kaneko, S. Goto, S. Ono, T. Hirai,
H. Kudo, M. Shigekawa, A. Shinohara, Y. Oura, H.
Nakahara, K. Sueki, H. Kikunaga, N. Kinoshita, N. Tsuruga,
A. Yokoyama, M. Sakama, S. Enomoto, M. Schädel, W.
Brüchle, and J. V. Kratz, J. Am. Chem. Soc. 126, 5219 (2004).
(14) Y. Nagame, M. Asai, H. Haba, S. Goto, K. Tsukada, I.
Nishinaka, K. Nishio, S. Ichikawa, A. Toyoshima, K.
Akiyama, H. Nakahara, M. Sakama, M. Schädel, J. V.
Kratz, H. W. Gäggeler, and A. Türler, J. Nucl. Radiochem.
Sci. 3, 85 (2002).
(15) J. V. Kratz, M. K. Gober, H. P. Zimmermann, M. Schädel,W. Brüchle, E. Shimpf, K. E. Gregorich, A. Türler, N. J.
Hannink, K. R. Czerwinski, B. Kadkhodayan, D. M. Lee,
M. J. Nurmia, D. C. Hoffman, H. W. Gäggeler, D. Jost, J.
Kovacs, U. W. Scherer, and A. Weber, Phys. Rev. C 45,
1064 (1992).
(16) A. Türler, R. Dressler, B. Eichler, H. W. Gäggeler, D. T.
Jost, M. Schädel, W. Brüchle, K. E. Gregorich, N.
Trautmann, and S. Taut, Phys. Rev. C 57, 1648 (1998).
(17) P. A. Wilk, K. E. Gregorich, A. Türler, C. A. Laue, R.
Eichler, V. Ninov, J. L. Adams, U. W. Kirbach, M. R. Lane,
D. M. Lee, J. B. Patin, D. A. Shaughnessy, D. A. Strellis,
H. Nitsche, and D. C. Hoffman, Phys. Rev. Lett. 85, 2697
(2000).
(18) A. Türler, Ch. E. Düllmann, H. W. Gäggeler, U. W.
Kirbach, A. B. Yakushev, M. Schädel, W. Brüchle, R.
Dressler, K. Eberhardt, B. Eichler, R. Eichler, T. N. Ginter,
F. Glaus, K. E. Gregorich, D. C. Hoffman, E. Jäger, D. T.
Jost, D. M. Lee, H. Nitsche, J. B. Patin, V. Pershina, D.
Piguet, Z. Qin, B. Schausten, E. Shimpf, H.–J. Schött, S.
Soverna, R. Sudowe, P. Thörle, S. N. Timokhin, N.
Trautmann, A. Vahle, G. Wirth, and P. M. Zielinski, Eur.
Phys. J. A 17, 505 (2003).
(19) Yu. Ts. Oganessian, A. V. Yeremin, G. G. Gulbekian, S. L.
Bogomolov, V. I. Chepigin, B. N. Gikal, V. A. Gorshkov,
M. G. Itkis, A. P. Kabachenko, V. B. Kutner, A. Yu.
Lavrentev, O. N. Malyshev, A. G. Popeko, J. Rohác, R. N.
Sagaidak, S. Hofmann, G. Münzenberg, M. Veselsky, S.
Saro, N. Iwase, and K. Morita, Eur. Phys. J. A 5, 63 (1999);
Yu. Ts. Oganessian, A. V. Yeremin, A. G. Popeko, O. N.
Malyshev, A. V. Belozerov, G. V. Buklanov, M. L.
Chelnokov, V. I. Chepigin, V. A. Gorshkov, S. Hofmann,
M. G. Itkis, A. P. Kabachenko, B. Kindler, G. Münzenberg,
R. N. Sagaidak, S. Saro, H.-J. Schött, B. Streicher, A. V.
Shutov, A. I. Svirikhin, and G. K. Vostokin, Eur. Phys. J. A
19, 3 (2004).
(20) H. W. Gäggeler, D. T. Jost, U. Baltensperger, A. Weber, J.
Kovacs, D. Vermeulen, and A. Türler, Nucl. Instr. Methods
A 309, 201 (1991).
(21) R. Eichler, B. Eichler, H. W. Gäggeler, D. T. Jost, D.

210 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005
Piguet, and A. Türler, Radiochim. Acta 88, 87 (2000).
(22) V. Pershina and T. Bastug, J. Chem. Phys. 113, 1441 (2000).
(23) Y. Nagame, K. Tsukada, M. Asai, A. Toyoshima, K.
Akiyama, Y. Ishii, T. Kaneko-Sato, M. Hirata, I. Nishinaka,
S. Ichikawa, H. Haba, S. Enomoto, K. Matsuo, D. Saika, Y.
Kitamoto, H. Hasegawa, Y. Tani, W. Sato, A. Shinohara, M.
Ito, J. Saito, S. Goto, H. Kudo, H. Kikunaga, N. Kinoshita,
A. Yokoyama, K. Sueki, Y. Oura, H. Nakahara, M. Sakama,
M. Schädel, W. Brüchle, and J. V. Kratz, Radiochim. Acta93, 519 (2005).
(24) M. Schädel, W. Brüchle, E. Jäger, E. Schimpf, J. V. Kratz,
U. W. Scherer, H. P. Zimmermann, Radiochim. Acta 48,
171 (1989).
(25) A. Toyoshima, H. Haba, K. Tsukada, M. Asai, K. Akiyama,
I. Nishinaka, Y. Nagame, D. Saika, K. Matsuo, W. Sato, A.
Shinohara, H. Ishizu, M. Ito, J. Saito, S. Goto, H. Kudo, H.
Kikunaga, N. Kinoshita, C. Kato, A. Yokoyama, and K.
Sueki, J. Nucl. Radiochem. Sci. 5, 45 (2004).

Nagame(26) P. M. Plaisance, R. Guillaumont, Radiochim. Acta 12, 32(1969).
(27) J. I. Kim, H. Lagally, H.-J. Born, Anal. Chim. Acta 64, 29(1973).
(28) J. Korkisch, Handbook of Ion Exchange Resins: Their
Application to Inorganic and Analytical Chemistry, CRC
Press, Boca Raton, FL, 1989.
(29) M. Hirata, private communication.
(30) Ch. E. Düllmann, W. Brüchle, R. Dressler, K. Eberhardt,
B. Eichler, R. Eichler, H. W. Gäggeler, T. N. Ginter, F.
Glaus, K. E. Gregorich, D. C. Hoffman, E. Jäger, D. T.
Jost, U. W. Kirbach, D. M. Lee, H. Nitsche, J. B. Patin, V.
Pershina, D. Piguet, Z. Qin, M. Schädel, B. Schausten, E.
Schimpf, H.-J. Schött, S. Soverna, R. Sudowe, P. Thörle, S.
N. Timokhin, N. Trautmann, A. Türler, A. Vahle, G. Wirth,A. B. Yakushev, and P. M. Zielinski, Nature, 418, 859(2002).