Study of pair transfer in 134Sn via 132Sn(t,p) 134Sn reac9on Spokespersons (if several, please use capital le<ers to indicate the name of the contact person): O. SORLIN (GANIL), K. Wimmer (NSCL/MSU) Address of the contact person: GANIL Phone: 33 2 31 45 45 25
Fax: E-­‐mail: [email protected]
IPN Orsay : M. Assié, D. Beaumel, N de Séréville, S. Franchoo, M. Grasso, F. Hammache, E. Kahn, J.
Margueron, I. Stefan
GANIL : B. Bastin, L. Cáceres, F. de Oliveira, G. F. Grinyer, D. Lacroix, M. Ploszajczak, H. Savajols,
J.C. Thomas
IKS Leuven : P. Van Duppen, T. Roger, R. Raabe, M. Huyse
IRFU: T. Duguet, F. Flavigny, A. Gillibert, V. Lapoux, L. Nalpas, A. Obertelli, E. Pollacco
CEA/DAM : L. Gaudefroy, V. Méot, O. Roig
IReS Strasbourg : R. Lozeva, F. Nowacki, K. Sieja
Complementary to proposals
Univ. Surrey : W. Catford
Univ Santiago de Compostela : B. Fernandes Dominguez
V. Lapoux ; D. Beaumel
Triumf : R. Krücken
TU Darmstadt : T. Kroell
Brief summary of the physics goal : Pair transfer is proven to be a useful tool to study interesting nuclear structure aspects
especially to study the pairing interaction. With the possibility to post-accelerate beams of
weakly bound nuclei, two-neutron pair transfer have been investigated as in the case of
6,8He. The use of singly magic neutron-rich Sn isotopes offers an alternative mean to
probe the very nature of the pairing interaction between two neutrons. The idea of the
present proposal is to achieve pair transfer using (t,p) reaction at 8 A.MeV into the
weakly bound 3p3/2 and 3p1/2 orbits in the 134Sn (Day1) and 136Sn (Day2) nuclei. These
transfer reactions could be compared to that in the more bound 2f7/2 orbit, with the aim of
probing how the pair transfer is influenced by the nuclear diffuseness and the virtual
scattering of pairs to the continuum. of
Questions
V(r)
?
r
Is the pairing a surface/volume mode ?
-> superfluidity in neutron stars
(M. Fortin, J. Margueron et al.)
How is pair scattering occuring to continuum states?
‘Very interesting but unpredictible !’
Mean Use pair transfer to states lying close to continnum having
- large radial extension (3p states)
- large cross section (transfer to low  much favored)
Where ?
Neutron-rich Sn isotopes around 132Sn
Predicted shell evolution in the Sn isotopic chain
N=90 gap created by nn interactions
(see V. Lapoux proposal)
ESPE(n)
Sn
3p,2f states are pure s.p. states at N=83
(see Jones et al. Nature 2010)
134Sn
0+2
2+
0+ (2f7/2)2
g.s.
*
0 f5/2
1.3
1.48
p1/2
p3/2
N=90
-2 f
7/2
SM calc K. Sieja
Are 3p close to high j states?
Are high j states bound in 133Sn?
h9/2 i3/2
f5/2
occup.
-4
YES : Low (3p)2 component in 0+2,3
-6
BUT depends on pair transfer to continuum
NO : Large (3p)2 component in 0+2,3
~3MeV
0+3
config. energy
?
3.23
(3p3/2)2 2.36
Derived in analogy to Ca
132Sn
f7/2
140Sn
82
Neutron number 90
-> Study pair transfer to 0+ -> determine their 3p,2f content …
Two neutron transfer reaction to probe pairing interaction
Sn
5/2
1/2 3/2 -
-
7/2 Q=-3.79MeV 133Sn
0+
0+ (3p1/2)2 ?
0+ (3p3/2)2
Wimmer et al. PRL 105 (2010)
2+
0 + (2f7/2)2
134Sn
Q=-2.09MeV
132Sn
Calc. K. Wimmer for (p1/2)2
Determine final spin state
-> proton angular distributions -> Δ"
30Mg(t,p)32Mg
@ISOLDE
sim
seq
total
Distinguish between seq and simult transfer
-> Distortion of angular distribution
Technical feasibility
Weak cross section 10-2mb/sr -> need large efficiency -> Gaspard
At 106pps -> 22 protons /h for tritium target 40 µg.cm-2 -> 25 UT
Gaspard with γ array (10% efficiency) to distinguish between neighbouring states
HUGE fusion cross section with target holder Ti -> spectrometer / beam catcher
Probing the structure of the island of inversion
30Mg(t,p)32Mg
neutron pair transfer
1058
886
32Mg
0+2
2+
0+
p3/2, f7/2
d3/2
d3/2
g.s.
Wimmer et al. PRL 105 (2010)
1st excited