**Neutron
transfer
reactions at large internuclear distances studied with the
PRISMA spectrometer
and the AGATA demonstrator**, D. Montanari, *Università
degli Studi di Padova - INFN Padova, Italy* − Two-nucleon
transfer reactions
play a key role in investigating correlations between nucleons
in nuclei. With
heavy ion reactions, multiple transfer
of nucleons become available, giving the possibility to compare
the relative
role of single particle and pair transfer modes [1]. Below the Coulomb
barrier, nucleons are
transferred in a restricted excitation energy window and, at
large internuclear
distances, the interacting nuclei are slightly influenced by the
nuclear
potential. These
conditions allow to
diminish the complexity of theoretical calculations and thus to
extract more
quantitative information on pair correlations [2,3].

Using
the
large solid angle magnetic spectrometer PRISMA, at the
Laboratori Nazionali
di Legnaro, a first reaction at sub-barrier energies has been
performed in
inverse kinematics for the closed shell system ^{96}Zr+^{40}Ca
[4].
An excitation function ranging from above to well below the
Coulomb
barrier has been measured and transfer probabilities [5] have
been extracted
for the neutron transfer channels.
The
comparison between data and microscopic calculations shows the
importance
played by transitions to 0+ excited states and of states with
high
multipolarity and non natural parity.

As
a
next step, we recently measured an angular distribution of the
transfer
channels in the reaction ^{60}Ni+^{116}Sn,
using PRISMA coupled
to the AGATA demonstrator gamma array. In
this superfluid system the ground state Q-values for the neutron
transfer
channels are close to their optimum Q-values.
It is therefore interesting to study the behavior of the
transfer
probabilities compared with the previously measured closed shell
system and to
compare the results with the same kind of theoretical
calculations.

On
the
basis of an event-by-event reconstruction of the ion
trajectories inside
the PRISMA spectrometer [6], the projectile-like fragments have
been fully
identified in atomic number Z, mass A and Q-value, leading to
the determination
of the transfer cross sections. The AGATA demonstrator, whose
detected gamma
rays are Doppler corrected taking into account the vector
velocity measured
with PRISMA, has been employed to extract the transfer strength
to excited
states.

In
this
talk the results of these recent measurements will be presented,
and a
discussion will be made on the possibilities offered in the
field by exploiting
large solid angle spectrometers.

[1]
R.A. Broglia and
A. Winther, "Heavy Ion Reactions", Addison-Wesley Pub. Co.,
Redwood
City CA, 1991.

[2]
B. F. Bayman and
J. Chen, Phys. Rev.
C**26**, 1509 (1982).

[3]
G. Potel, F.
Barranco, E. Vigezzi and R. A. Broglia, Phys. Rev. Lett. **105**, 172502 (2010).

[4]
L. Corradi et
al., Phys Rev. C **84**,
034604 (2011).

[5]
W. von Oertzen
and A.Vitturi, Rep. Prog. Phys. **64**,
1247 (2001).