The Predicted and Observed Properties of Eka

Nuclear Structure of
Actinide and Transactinide
Elements
Irshad Ahmad
Argonne National
Laboratory
September 11, 2011
Superheavy Elements
•
Lanthanides (Rare Earths): La (Z = 57) to Lu (Z = 71)
Filling of 4f shell …. 14 elements
•
Actinides: Ac (Z = 89) to Lr (Z = 103)
Filling of 5f shell …. 14 elements
•
Transactinide Elements: Elements Rf (Z = 104) and beyond
•
Superheavy Elements: Definition not as definite
Elements around Z = 114
Discovery of Transuranium Elements
1940-1955 Berkeley
Np (Z = 93) – Md (Z = 101)
Actinide targets + d or alpha
60-inch cyclotron
Identification: Chemical separation
1960’s Dubna/Berkeley
No (Z = 102) – Sg (Z = 106)
Heavy-ion beams on actinide targets
Identification; Decay chain
1980-1990 GSI, Germany
Bh(Z = 107) – Cn (Z = 102)
Cold fusion, 208Pb/209Bi targets + HI beams
Identification: Decay chain to known isotope
2004 Riken, Japan
Z=113 , 209Bi+HI beam
Identification: Decay chain
2000’s Dubna, Russia
Z = 114 – Z = 118
Hot fusion, actinide targets + 48Ca beam
Identification: Decay chain; end product unknown isotope
Half lives of the longest-lived isotopes of actinides
Atomic Radii
Atomic Radii
Atomic ionization energy
Nuclear energy levels
Total Energy
E(β) = ELDM(β) +  u(β) + P(β)
p,n
Shell Correction
u(β) = u – ũ
u =  2
 – single-particle energy
– pair occupation probability

ũ = 2  g()d

g() – uniform distribution of nuclear states
– chemical potential

N = 2  g()d

N = total number of particles
GSI, Germany Linac + Ship
Discovered element 107-112
Example: Hassium (Z = 108), 1995
208Pb
265Hs
+ 58Fe  265Hs + n
separated from the beam and other reaction products
Using recoil separator SHIP
Alpha counted 265Hs and its daughter
Dubna, Russia, Cyclotron
Discovered element Z = 114-118
48Ca
beam plus actinide targets
Example: Element 117
249Bk
+ 48Ca 
294 X
117 +3n
Measured alpha decay energy and fission followed the decay chain
Final isotope not known
Phys. Rev. Lett. 104, 142502 (2010)
255Fm
nucleus
R
j
Symmetry
Axis
Wp[NnzLS]
e.g. 7/2+[613]
W
odd-mass
K+3
6+
K+2
K+1
K
4+
for j=9/2
W=1/2, 3/2, 5/2, 7/2 and 9/2
2+
0+
even-even
protons
neutrons
Differential Cross Sections in (d,p)
reactions on deformed nuclei
dσ/dΩ = 2N u2KCjK2ΘDW
with u2K= 1 - v2K; v2K= pair occupation probability;
CjK= the expansion coefficient of the wavefunction
ψK= ΣjCjKΦjK
ΘDW = DWBA cross section
N=normalization constant
ΣCjK2 = 1 and CjK2 = dσ/dΩ /(k ΘDW)
Cjk2 for Neutron Single-Particle States above
N=152
Chasman (1990)
State
K
j
1/2
3/2
5/2
7/2
9/2
11/2
13/2
0.041
0.209
0.216
0.238
0.133
0.030
0.003
0.843
0.102
0.049
0.358
0.161
0.196
0.024
9/ 2+[615]
0.069
0.914
0.016
9/ 2+[604]
0.910
0.076
0.009
1/ 2+[620] 0.131
7/ 2+[613]
3/ 2+[622]
0.168
0.091
October Issue
T1/2=0.9 ms
294118
T1/2=1.0 ms
Summary
 Use of decay data and one-nucleon transfer
reaction data have enabled us to determine
the single-particle energies and wavefunctions
in very heavy actinide nuclei.
– Neutron orbitals up to N=162 identified
– Proton orbitals up to Z=101 identified
 The single-particle energies and
wavefunctions are reproduced by a singleparticle model calculation using a deformed
Woods-Saxon potential.
Acknowledgement
This work was supported by the U.S. Department of Energy, Office of Nuclear
Physics, under contract No. DE-AC-02-06CH11357.
Participants
I. Ahmad, F.G. Kondev, M. P. Carpenter, R. R. Chasman,
J. P. Greene, E.F. Moore, R. V. F. Janssens, T. Lauritsen,
C. J. Lister, and D. Seweryniak
Discovery of the First Transuranium
Element - Neptunium
Irshad Ahmad
Argonne National Laboratory
September 12, 2011
Mendeleeff’s Table I.-1871
Series
Group I.
R2 O
Group II
RO
Group III
R2O3
Group IV
RH4
RO2
Group V
RH3
R2O6
Group VI
RH2
RO3
Group VII
RH
R2O7
1…..
H=1
2…..
Li=7
Be=9.4
B=11
C=12
N=14
O=16
F=19
3…..
Na=23
Mg=24
Al=27.3
Si=28
P=31
S=32
Cl=35.5
4…..
K=39
Ca=40
-=44
Ti=48
V=51
Cr=52
Mn=55
5…..
(Cu=63)
Zn=65
-=68
-=72
As=75
Se=78
Br=80
6…..
Rb=85
Sr=87
Y=88
Zr=90
Nb=94
Mo=96
-=100
7…..
(Ag=108)
Cd=112
In=113
Sn=118
Sb=122
Te=125
I=127
8…..
Cs=133
Ba=137
Di=138
Ce=140
….
….
….
….
9…..
….
….
….
….
….
….
….
….
10…..
….
….
Er=178
La=180
Ta=182
W=184
….
Hg=200
Tl=204
Pb=207
Bi=208
….
….
…..
….
Th=231
….
U=240
….
11…..
12…..
(Au=199)
….
Group VIII
RO4
Fe=56,Ce=59,
Ni=59, Cu=63
Ru=194, Rh=104,
Pd=106, Ag=108
Os=195, In=197,
Pt, 198, Au=199
…..
33
The Predicted and Observed Properties of Eka-silicon (Germanium)
Property
Relative atomic mass
Eka-silicon
1871 prediction
Germanium
discovered 1886
72
72.32
Specific gravity
Specific heat
5.5
0.073
Atomic volume
Color
13 cm3
Dark gray
5.47
0.076
13.22 cm3
Grayish white
•
•
•
1932 Neutron discovered by Chadwick
1934 Artificial radioactivity discovered by I. Curie and F. Joliet
1934/35 Fermi irradiated more than 50 elements with neutrons Ra + Be ~107 n/s
For each element, n capture made beta unstable isotope which decayed to
the next element with one more proton
For example: 197Au + n  198Au (2.7 d)  198Hg
So U + n should produce element with Z = 93
238U + n  239U  239Np
In the irradiation of U Fermi observed activities with
239Np half-life = 2.3 days
Half-life = 40 s, 1 min, 15 min, 90 min
Performed chemical separation with the 15-min activity. It was carried with Mn. So it
was Re-like as expected for Np. Now we know that what Fermi saw was 14.3-min
101Tc. So Fermi saw no Np at all!!
Lawrence at Berkeley
1931
4.5 inch cyclotron
80 keV
11 inch cyclotron
1.2 MeV
1936
27 inch cyclotron
6 MeV d
1937
37 inch cyclotron
8 MeV d
1939
60 inch cyclotron
22 MeV d
8 MeV d + Be
•
16 MeV d + Be gives 1011 n/s/microampere
•
This is 10,000 times neutron production with Ra + Be
Medical Use:
131I
gives
1010 neutrons/s/microampere
•
(8 d) , 59Fe (45 d), 99Tc (6 hr),
60Co
(5.3 yr)
History of the discovery of Neptunium
•
1939 Fission discovered. This showed Fermi’s discovery of element 93 was wrong
•
1939 McMillan: thin U + neutrons from 37-inch cyclotron. Fission fragments
recoiled out of the target. Two activities remained in the target. Half-life = 23 min;
Hahn showed it to be 239U in 1937.
So, 2.3-d activity, most likely Z = 93
•
1939 Segre performed chemical separation. Chemistry not like Re so, no element
93 Chemistry more like Rare earths
•
1940 McMillan and Abelson: chemistry
Chemistry like U, different from any known element.
Showed 2.3-d activity grew with the half-life of 239U (23 min)
So, it is Z = 93, named neptunium
Discovery of Neptunium
Chemical separation by McMillan and Abelson showed that:
•
Element 93 (Np) is not like Re
•
It is like U and Rare earth
•
Thus Np should be part of actinide series (5f)
•
This concept was further developed by Seaborg
•
So, now they had predictions of chemical properties of elements
beyond neptunium (Np)
Discovery of Element with Z = 101, Md
•
Chemistry of Lanthanides showed what the chemistry of Md would be like
•
On a cation-exchange resin column it would elute before Fm.
•
Experiment: only 109 atoms of 253Es available (1 picogram)
253Es
•
+ 4He  256Md + n
Collect the recoils, dissolved in acid and loaded on a But column
Md separated
Only 5 atoms identified
Chemistry behaved perfect!
Phys. Rev. 98, 115 (1955)
Acknowledgement
This work was supported by the U.S. Department of Energy, Office of Nuclear Physics,
under contract No. DE-AC02-06CH11357.