Measurement of the Isoscalar Monopole Response in the Neutron-Rich Nucleus $^{68}$Ni using the active target MAYA
Résumé
We report the measurement of the isoscalar monopole strength in the unstable nucleus $^{68}$Ni using
inelastic alpha scattering at 50AMeV in inverse kinematics. This experiment has been performed at
GANIL with LISE spectrometer using a dedicated detector: the active target MAYA. A part of the
isoscalar giant monopole resonance (ISGMR) has been measured at 21:1 $\pm$ 1:9MeV and indications
for a soft monopole mode are provided for the first time at 12:9 $\pm$ 1:0MeV. Distorted-wave born ap-
proximation (DWBA) with random-phase approximation (RPA) transition densities have been used
to study angular distribution and indicate that the L = 0 multipolarity dominates the cross-section for
the ISGMR, and significantly contributes to the soft mode.