Coulomb barrier distributions:
puzzles and recent experiments
Eryk Piasecki
and
The Barrier CollaborationSeptember 2006
Determination of importance of various couplings (vibrational, rotational, single-particle ones) in different reaction and systems.
What is the influence of the Q of reaction?
What is the influence of formfactors?
Determination of the nuclei deformation parameters (2, 3, 4 and perhaps even 6), including their sign, what is pretty difficult using the standard Coulomb excitation methods.
Reliable calculation of the nucleus-nucleus cross-sections in sub-barrier region.
Optimization of superheavy elements production.
Investigation of the influence of exotic nuclear structures (e.g. “halo”) on the reaction mechanisms.
Motivation (hopes)
Two experimental methods:
fusfus EdE
dED
2
2
Ruth
qeqe dE
dED
42 44 46 48 50 52 54 56 58 600.1
1
10
100
1000
fus
[mb]
Ecms
[MeV]
42 44 46 48 50 52 54 56 58 600.0
0.2
0.4
0.6
0.8
1.0
qe/
Rut
h
Eeff
[MeV]
Shape of 20Ne
Cluster
model
Predictions of Coupled Channels Theory
for 20Ne + 118Sn(CCFULL code)
No couplings
With couplings
Suspicion: perhaps the „weak” channels (transfers,
s.p. excitations) are not that weak as it is assumed
in the CC calculations?
What we miss in the calcs???
0,92 0,96 1,00 1,04 1,08 1,12 1,161E-4
1E-3
0,01
0,1
22Ne
20Ne
16-12-2005 00:45:32
Transfer in 20,22Ne + 118Sn
-
tran
sfer
/ to
tal b
acks
catte
ring
Eeff
/B [MeV]
20Ne; Tel1+3+4 (160o)
20Ne; Tel2 (120o)
22Ne; Tel1+3+4 (160o)
22Ne; Tel2 (120o)
50 55 60 65 70
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
50 55 60 65 70
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
30 35 40 45
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
30 35 40 45
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
exp. data inert
CC: 4(20Ne)=0.27
Ne(0+,2+,4+,6+) x Sn(0+,2+,2ph);
2(Ne) = 0.46,
2(Sn) = 0.13
20Ne + 118Sn
Dqe
[MeV
-1 ]
CC: 4(22Ne)=0.10
20-09-2006 21:24:10
22Ne + 118Sn
Dqe
[MeV
-1 ]
Eeff
[MeV]
22Ne + natNi
20Ne + natNi
Eeff
[MeV]
20Ne+58Ni 20Ne+118Sn 22Ne+118Sn0
50
100
150
200
250
300
-1n -2n +1n +2n -1p +1p -1
Ca
lc. t
ran
sfe
r cr
oss
se
ctio
ns
[mb
]
Projectile + Target
Estimated from systematics
20Ne+58Ni 20Ne+90Zr 20Ne+92Zr 20Ne+118Sn 20Ne+208Pb0
50
100
150
200
250
300
Near-barrier energy25-12-2005 19:21:18
-1n -2n +1n +2n -1p +1p -1
Ca
lc. t
rans
fer
cros
s se
ctio
ns [m
b]
Projectile + Target
Estimated from systematics
40 42 44 46 48 50 52 54 56 58 60 620.00
0.05
0.10
0.15
0.20
90Zr
Dqe
40 42 44 46 48 50 52 54 56 58 60 620.00
0.05
0.10
0.15
0.20
90Zr
Dqe
40 42 44 46 48 50 52 54 56 58 60 620.00
0.05
0.10
0.15
0.20
92Zr
Dqe
Eeff
[MeV]
Expectations & experimental results:20Ne + 90Zr:
weak neutron
transfer
barrier structure
20Ne + 92Zr:
stronger neutron
transfer
no structure
wider barrier distribution
Open questions:
Transfers and/or s.p. exciations?
Quantitative relation between the strength of „weak” channels and barrier smoothing
Why the barrier structure has been observed in many experiments?
Is Dfus as sensitive for smoothing as Dqe?
CC treatment of these problems
Is the puzzle solved??
84 88 92 96 100 1041E-3
0.01
0.1
1
10
100
1000
84 88 92 96 100 104
0.0
0.2
0.4
0.6
0.8
1.0
84 88 92 96 100 1040.00
0.05
0.10
0.15
0.20
2005-09-01 08:40:1920Ne + 208Pb (CC calculations)
fus [
mb
]
q
e/R
uth
fusion qe
Dqe; D
fus
[Me
V-1]
Ecms
[MeV]
JYUAug/Sept. 2006
Simultaneous measurements of Dfus & Dqe
E
MCP START
beam
20Ne
Target
natNi90,92Zr
118Sn
206,208Pb
(E,ToF) A
LToF = 55cm
FWHMToF ≈ 200ps
Measurements of weak channels strengths
(transfers & s.p. excitations)
Conclusions:
•The weak channels can have quite considerable influence on the barrier height distributions
•There are still some (interesting) open questions
Transfers and/or s.p. exciations?
Quantitative relation between the strngth of „weak” chanels and barrier smoothing
Why the barrier structure has been observed in many experiments?
Is Dfus as sensitive for smoothing as Dqe?
Some of the answers are probably already in our hands and will be presented soon.
CC treatment of these problems is badly needed
September 2006
The BARRIER Collaboration:Warsaw University (Inst. Exp. Phys. & Heavy Ion Lab):
Ł.Świderski, P. & T. Czosnyka, J.Jastrzębski, A.Kordyasz, M.Kowalczyk, M.Kisieliński, K.Piasecki, E.Piasecki
Białystok University: T.Krogulski
Technische Universitat (Darmstadt): M.Mutterer
Radium Institute (St. Petersburg): S.Kchlebnikov, G.Turin
University of Jyvaskyla: W.Trzaska, M. Sillanpää
Tohoku University: K.Hagino
IReS (Strasbourg): N.Rowley
Inst. Nucl. Studies (Warsaw): K.Rusek
LNL (Legnaro): A.Stefanini
LNS (Catania): P.Russotto
JINR (Dubna): E.Kozulin, S.Smirnov
Kurchatov Inst. (Moscow): A.Ogloblin, S.Dmitriev