Frontiers in Science II 2013.11.6

Physics of superheavy elements
Kouichi Hagino
Nuclear Theory Group,
Department of Physics,
Tohoku University
 What is nuclear physics?
 What are superheavy elements?
 How to create superheavy elements?
 What are chemical properties of superheavy elements?

Introduction: atoms and atomic nuclei
What would you see if you magnified the dog?

~ 50 cm

Introduction: atoms and atomic nuclei
cells~ 50 cm~ m = 10-6 m

Introduction: atoms and atomic nuclei

DNAcells~ 50 cm~ 10-8 m~ m = 10-6 m
atomAll things are made of atoms.

~ 10-10 m

All things are made of atoms.

••••

Thales, Democritus (ancient Greek)
Dalton (chemist, 19th century)
Boltzmann(19th century)
Einstein (1905)~ 10-10 m
STM image(surface physics group,Tohoku university)

Introduction: atoms and atomic nuclei

DNAcells~ 10-8 m~ 50 cm
atomatomic nucleus~ 10-15 m~ 10-10 m

proton (+e)

neutron (no charge)

electron cloud (-e)

Neutral atoms: # of protons = # of electrons
Chemical properties of atoms# of electronsMp ~ Mn ~ 2000 Methe mass of atom ~ the mass of nucleus

Periodic table of chemical elements

tabular arrangement of chemical elements based on
the atomic numbers (= # of electrons = # of protons)

What are we made of ?
oxygen 43 kg
carbon 16 kghydrogen 7 kg
nitrogen 1.8 kg
calcium 1.0 kg
phosphorus 780 g
potassium 140 gsulphur 140 g
sodium 100 gchlorine 95 gmagnesium 19 giron 4.2 g
fluorine 2.6 gzinc 2.3 gsilicon 1.0 g
rubidium 0.68 gstrontium 0.32 g
bromine 0.26 glead 0.12 gcopper 72 mg
aluminium 60 mg
cadmium 50 mgcerium 40 mg
barium 22 mg
iodine 20 mg
tin 20 mg
titanium 20 mg
boron 18 mg
nickel 15 mg
selenium 15 mg
chromium 14 mg
manganese 12 mg
arsenic 7 mg
lithium 7 mg
caesium 6 mg
mercury 6 mg
germanium 5 mg
molybdenum 5 mg
cobalt 3 mg
antimony 2 mg
silver 2 mg
niobium 1.5 mg
zirconium 1 mg
lanthanum 0.8 mg

gallium 0.7 mg
tellurium 0.7 mg
yttrium 0.6 mg
bismuth 0.5 mg
thallium 0.5 mg
indium 0.4 mg
gold 0.2 mg
scandium 0.2 mg
tantalum 0.2 mg
vanadium 0.11 mg
thorium 0.1 mg
uranium 0.1 mgsamarium 50 µg
beryllium 36 µg
tungsten 20 µg

proton (+e)

neutron (no charge)

Where are neutrons?

Nuclear Chart: 2D map of atomic nuclei

protonnumberneutron number

Nuclear Chart: 2D map of atomic nuclei

protonnumberisotopes
16O (Z=8, N=8, A=16)
17O (Z=8, N=9, A=17)
18O (Z=8, N=10, A=18)
A=Z+N

neutron number

・Stable nuclei in nature： 287
・Nuclei artificially synthesized ：about 3,000
・Nuclei predicted：about 7,000 ~ 10,000

protonnumberNuclear Physics:
Several static anddynamical propertiesof those nuclei
neutron number

Nuclear Chart: 2D map of atomic nuclei

protonnumberhow many neutrons can be attached?
what is the shape of nuclei?
is there any exotic structure?
what is the heaviest nucleus?
how do nuclei decay?
….. etc. etc.
neutron numberAn example of what we investigate in nuclear physics
what is the shape of a nucleus?

Are nuclei all spherical?

what is the shape of nucleus?

http://t2.lanl.gov/tour/sch001.html

Some nuclei are deformed in the ground state!
what are combinations of (Z,N) which yield a deformation?

Periodic table of chemical elements

What is the heaviest element?

Periodic table of chemical elements

What is the heaviest element?
natural elements: Pu (Z=94)
U (Z=92)

a tiny amount in nature
What determines these numbers??

natural elements:

What is the heaviest element?
Pu (Z=94)
a tiny amount in nature
U (Z=92)

What determines these numbers??
heavy nuclei

large Coulomb repulsion
unstable against  decay
4He nucleus=  particle+(Z,N)(Z-2,N-2)(Z=2,N=2)

Decay half-lives of heavy nuclei13.7 billion years

4.6 billion years

232Th

1.405 x 1010 years
238U 4.468 x 109 years
244Pu 8.08 x 107 years
247Cm 1.56 x 107 years

Heavier nuclei: unstable against fission

Periodic table of chemical elements

artificially synthesized (‘man-made’)
nuclear reactions

superheavy elements (SHE)Prediction of island of stability: an important motivation of SHE study

island of stability around Z=114, N=184

Yuri Oganessian

W.D. Myers and W.J. Swiatecki (1966), A. Sobiczewski et al. (1966)

modern calculations: Z=114,120, or 126, N=184e.g., H. Koura et al. (2005)

Island ofstability(SHE)

Thorium

Uranium

LeadContinent

Yuri Oganessianwho is she?

Z=110
Z=111
Z=112
Z=113
Z=114
Z=115
Z=116
Z=117
Z=118

Darmstadtium (Ds) 1994 Germany
Roentgenium (Rg) 1994 Germany
Copernicium (Cn) 1996 Germany
No name yet
2003 Russia / 2004 Japan
Flerovium (Fl)1999 Russia (*)
No name yet
2003 Russia
Livermoriun (Lv) 2000 Russia
No name yet
2010 Russia
No name yet
2002 Russia(*)
island of stability: Z=114, N=184
Fl discovered: Z=114, N=174-175
island not yet confirmed

How to synthesize SHE?
Nuclear fusion reactions

two positive charges
repel each otherNnuclear attractive
intraction

compoundnucleus

Scf.
SN

accelerate a projectile
nucleus to overcome the barrier

e.g.,
70Zn + 209Bi

279113

contact

Quasi-fission

fusionCNfission

evaporation
ERn

experimentally detectedcannot distinguishexperimentally
CN = compound nucleus
ER = evaporation residue

typical values for Ni + Pb reaction
1011 = 100,000,000,000

99,999,000,000
106 = 1,000,000
CNvery rare
event !!

999,999

1ERn

experimentally detected

CN = compound nucleus
ER = evaporation residue

Element 113 (RIKEN, K. Morita et al.)70Zn (Z=30)+ 209Bi (Z=83)

278113 + n

K. Morita et al., J. Phys. Soc. Jpn. 81(‘12)103201
only 3 events for 553 days experiment

Theoretical treatment

Pcap
contact

Quasi-fission

PCN
fusionCNevaporation

fissionPsur
ERstatistical modeln

CN = compound nucleus
ER = evaporation residue

2-body potential
1-body potentialE
Pcap: quantum
mechanics
compoundnucleus

thermalmotionenergydissipation

Theory: Lagenvin approach
multi-dimensional extension of:

q: ・internuclear separation,・deformation,・asymmetry of the twofragments

: friction coefficient
R(t): random force

34S + 238U

Quasi-fission
(QF)

CNER

fusion-fissionnY. Aritomo, K.H., K. Nishio, S. Chiba, PRC85(’12)044614

34S + 238U

captureQuasi-fission(QF)

compoundERCNER

fusion-fissionnY. Aritomo, K.H., K. Nishio, S. Chiba, PRC85(’12)044614

Element 113
 Dubuna
48Ca + 243Am  288115 + 3n  284113 +  (2003)
48Ca + 249Bk  293117 + 4n  189115 +   285113 +  (2010)etc.
Hot Fusion: 48Ca projectile
RIKEN
70Zn + 209Bi  278113 + n (2004) Cold Fusion: 208Pb or 209Bi target

DubnaFlerov Laboratory of
Nuclear Reactions,
JINR, Dubna, Russia
about 120 km north of
Moscow
105Db (Dubnium)fission

evaporation

capturesurvival
Hot Fusion

Cold Fusion

Example48Ca + 243Am  4n

70Zn+209Bi  1nasymmetry

large

small

Capture

large

small

Survival

small

large

 ~ fb = 10-39 cm2
118
117

RIKEN
(Cold fusion)

249Bk + 48Ca  4n294118

Lv Lv

209Bi + 70Zn  n290116286Fl

114
3rd event Aug. 12 2012
113

112
111

known nuclides

272Rg
269Ds 270Ds 271Ds110
109

266Mt

108

263Hs 264Hs 265Hs 266Hs 267Hs107

261Bh 262Bh

264Bh

106

258Sg 259Sg 260Sg 261Sg 262Sg 263Sg

268Mt





278113103

255Lr 256Lr 257Lr 258Lr 259Lr 260Lr 261Lr 262Lr

102 254No 255No 256No 257No 258No 259No 260No
101 253Md 254Md 255Md 256Md 257Md258Md 259Md 260Md

282

283

273Ds

279Ds270Mt

274Mt 275Mt 276Mt

266Db 267Db 268Db

287SFDubna(Hot fusion) ~ pb = 10-36 cm2

278Mt

275Hs

269Hs 270Hs 271Hs271Sg

Cn Cn

278Rg 279Rg 280Rg 281Rg 282Rg

265Sg 266Sg

256Rf 257Rf 258Rf 259Rf 260Rf 261Rf 262Rf 263Rf

291

Fl

282113 283113 284113285113 286113

274Rg

270Bh 271Bh 272Bh

104CN277Cn

266Bh 267Bh

262Db 263Db
105 257Db 258Db 259Db 260Db 261Db 262

274Bh

270Db

267Rf

262No

cf. Cold Fusion:connected to known nuclei

100 252Fm 253Fm 254Fm 255Fm 256Fm 257Fm 258Fm 259Fm

ES 255Es 256Es 257Es

99

251Es 252Es 253Es 254

98

250Cf 251Cf 252Cf 253Cf 254Cf 255Cf 256Cf

CN287115 288115 289115290115

115

113

293117 294117

Hot Fusion:
neutron-richer CN

Naming rights?
Under discussions in the joint IUPAC/IUPAP Joint Working Party
IUPAC = International Union of Pure and Applied Chemistry
IUPAP = International Union of Pure and Applied Physics

RIKEN (Japan)
much less ambiguity with cold fusion
Dubna (Russia)
much larger number of events

Chemistry of superheavy elements

Are they here in the periodic table?
That is, does e.g., Lv show the same chemical properties
as O, S, Se, Te, and Po?

relativistic effect : important for large Z

E = mc2

Solution of the Dirac equation (relativistic quantum mechanics)
for a hydrogen-like atom:

relativistic effectFamous example of relativistic effects: the color of gold

Gold looked like silver if there was no relativistic effects!

5s

Rel.

Non-Rel.

Non-Rel.
Rel.

3.7 eV6s

2.4 eV
5d4d
Silver (Ag)Gold (Au)cf. visible spectrum
2.76 eV

3.7 eV

1.65 eV

2.4 eV

Rel.

Non-Rel.

Non-Rel.
Rel.

3.7 eVno colorabsorbed

2.4 eV

blue: absorbed
Silver (Ag)

AgGold (Au)Au

Chemistry of superheavy elements

How do the relativistic effects alter the periodic table for SHE?
a big open question

Summary
All things are made from atoms.
The heaviest natural elements are U/Pu.
Prediction: the island of stability
Superheavy elements (SHE) up to Z=118 have been synthesizedwith nuclear fusion reactions.
The fusion probability for SHE is extremely small.
The naming rights for Z=113: RIKEN or Dubna?
Chemistry of SHE: relativistic effects?

Homework Deadline: Wednesday, Nov. 13, 2013
 Submit the homework inside an envelope at #1047 (10th floor,Hagino’s office) in the Science Complex B building
or send it by e-mail to hagino@nucl.phys.tohoku.ac.jp.

1. Explain why it is so difficult to synthesize a superheavy element.
2. Write what you thought about the physics and chemistry ofsuperheavy elements and/or your impression on this lecture.