Search for Superheavy element and
Role of Fission Dynamics
 Z>92
(Heaviest Element in Nature) and upto Z=100-101
achieved by n irradiation or p, a, and d bombardment in
Cyclotron (1940-1955) (LBL)
 Z=102-106 by Light or Heavy-ion induced Fusion
-evaporation using heavy element targets (1958-1974)
Z=107-112 Heavy ion inuced fusion 208Pb,209Bi targets
(GSI)
Identified by recoil separation technique and connecting
to known daughter decay after implanting into Si strip
detectors.

Z=112-116 48Ca+Pu,Am,Cm,Cf (JINR, Dubna)
Identified
by gas filled separators
and Si strip setectors 1
March,
2006
SERC Course
March, 2006
SERC Course
2
March, 2006
SERC Course
3
March, 2006
SERC Course
4
March, 2006
SERC Course
5
Cross-section data and extrapolated values for cold-fusion
Reactions (1n -evaporation channel)
Cross-section increases with increasing isospin
March, 2006
SERC Course
6
March, 2006
SERC Course
7
E*~33 MeV
E*~34-38 MeV
48Ca+242Pu->287
March, 2006
114+3n
48Ca+244Pu->288
114+4n
SERC Course
48Ca+244Pu->289
114+3n
8
March, 2006
Yury Ts. OganessianPure Appl. Chem., Vol. 76, No. 9,
pp. 1715–1734,
SERC Course 2004.
9
March, 2006
SERC Course
10
48Ca+244Pu
March, 2006
SERC Course
11
March, 2006
SERC Course
12
The flight time of the reaction products through SHIP is 2 ms.
March, 2006
SERC Course
13
March, 2006
SERC Course
14
March, 2006
SERC Course
15
∙
Cold Fusion 208Pb and 209Bi targets bombarded by the following projectiles:
48Ca, 50Ti, 54Cr,58Fe, 62Ni, 64Ni, 70Zn, 76Ge, 82Se, and 86Kr.
∎
Hot Fusion 48Ca projectiles bombarded targets of 238U, 244Pu, 243Am,
245
March,
2006
SERC Course
Cm, 248Cm, and 249Cf,
16
BLDf gradually disappears
Spherical
Deformed
March, 2006
SERC Course
17
Fission barrier calculations of Smolanzuk et al.
106Sg
March, 2006
has highest barrier with half life of 3 hrs
SERC Course
18
March, 2006
SERC Course
19
For Z1Z2>1000 to 1650 depending
on the value of the charge
asymmetry, Zp/ZT.
Extra push energies
Swiatecki
March, 2006
SERC Course
20
No hindrance
Onset of fusion limitation
Due to Extra push energies
Effective fissility : weighted mean of mono-nuclear and binary
With weight for binary taken asSERC
1/3Course
March, 2006
21
March, 2006
SERC Course
22
Injection direction
Difference in energy
Between touching
Point and saddle point
Small due to shell structure
Of Ca and Pb
March, 2006
Fusion area inside
Saddle point
All trajectories reaches fusion
SERC Course
23
Quasi-fission is
dominant
Extra pocket in mass
Symmetric region
March, 2006
SERC Course
Deep
Quasifission
24

Evgeni A. Cherepanov
Brazilian Journal of
Physics, vol. 34, no. 3A,
September, 2004
The curve V (Z,L = 0) (for the value of R corresponding to
the pocket) has a few local minima, which reflect the shell
March, 2006
structure in the
interacting nuclei.
SERC Course
25
Mass asymm fluctuates
around 0.5 and then
relaxes quickly and
Trajectory move to main
pocket
48Ca+208Pb
EX=50 MeV
Aritomo and Ohta
Pre-print
March, 2006
SERC Course
Nuclear Physics A 744 (2004) 3–14
26
Critical stage
For FF mass
Asymmetries
large
Turning stage
For QF neck develops
and speeds up fission
keeping mass asymm.
For deep QF mass asymm
Relaxed in sub-pocket
At TS
March, 2006
48Ca+244Pu
Ex=50 MeV
SERC Course
27
March, 2006
SERC Course
28
The smaller formation probability due to inhibition of fusion
by competing mechanism:DIC,QF,FF,PEF
Asymmetric channels: higher E* and unfavourable for survival
March, 2006
SERC Course
29
Transition from
FF to QF
Mass distribution for
FF is asymmetric in shape
With peak around 132
QF
March, 2006
SERC Course
30
Measurements at LNL,Legnaro (Italy)
470-630 MeV
80Se
+ 208Pb
288
116
372 MeV
56Fe+232Th
470-630 MeV
80Se
+ 232Th
312124
Measurement of fragment mass and kinetic energy
and neutron correlations
March, 2006
SERC Course
31
Schematics of the setup for Se+Pb,Th experiment
March, 2006
SERC Course
32
80Se+208Pb
80Se+232Th
470 MeV
470 MeV
DIC dominates but significant events around symmetry
March, 2006
SERC Course
33
Se+Pb more asymmetric compared to Se+Th
QF is expected to be more for Se+Th
80Se+208Pb
80Se+232Th
470 MeV
103
103
470 MeV
510 MeV
550 MeV
630 MeV
Z = 50 N = 82
Z = 50 N = 82
d/dM (arb. units)
470 MeV
102
102
101
100
101
50
100
150
200
250
10-1
50
Mass (amu)
March, 2006
100
150
200
250
Mass (amu)
SERC Course
34
8000
cross sectionsXEcm (arb. units)
80
Se+208Pb (gated region)
80
Se+232Th (gated region)
Fit to Se+Pb data
Fit to Se+Th data
6000
higher extra-push energy
in the case of 80Se+232Th
4000
2000
0
0
March, 2006
20
40
60
80
100
120
Ecm-VSERC
Course
B (MeV)
140
160
180
200
35
80Se+208Pb
288116
50
40
30
tot
80Se+232Th
312124
50
20
40
10
30
tot
0
20
0
50
100
CN
Ex
150
200
250
10
(MeV)
0
ν sf tot =10±2 for Se+Pb
0
50
100
CN
Ex
150
200
(MeV)
12±1 for Fe+Th
March, 2006
=17±2 for Se+Th
SERC Course
36
250
on average of about 0.6 neutron per unit Z
March, 2006
SERC Course
37
an increase of about 0.54 neutron per unit Z
excitation energy gained by the system in its transition from the saddle to the
scission point (the term ΔEx by Hilscher) that is known to show a strong mass
and Z dependence.
March, 2006
SERC Course
38
JINR,Dubna
March, 2006
SERC Course
39
41 detectors of DEMON at Dubna
T. Materna et al. Nuclear Physics A734
(2004) 184-l 87
208±20
QF
FF
A/2±30
The pre-scission neutron multiplicity distribution simulated
using backtracing procedure show two components for Ca+Pu
Whereas for Ca+Pb only one component is seen
March, 2006
SERC Course
40
??
Self-consistent
Connectecd with
known species
March, 2006
SERC Course
41
Change from
Hot fusion to
Cold fusion
For higher N-Z
March, 2006
SERC Course
42
Survival probability
Depends on fission delay
And speed of cooling
Mainly by neutron
evaporation
March, 2006
SERC Course
43
March, 2006
SERC Course
44
March, 2006
SERC Course
45
Expected intensities s-1 for neutron-rich
radioactive beams
SPIRAL
HI based
PIAFE
Reactor based
24Ne
44Ar
78Zn
84Ge
94Kr
7 x 107
5 x 107
108
2 x 108
2 x 109
Region beyond Z= 114 needs beam intensities in
excess of 1014 s-1.
With MAFF and spallation facility with 100μA proton of 1GeV
Intensities may go up by 3 to 4 orders of magnitude
March, 2006
SERC Course
46
March, 2006
SERC Course
47