  Background: Double charge exchange (DCE) nuclear reactions have recently
attracted much interest as tools to provide experimentally driven information
about nuclear matrix elements of interest in the context of neutrinoless
double-beta decay. In this framework, a good description of the reaction
mechanism and a complete knowledge of the initial and final-state interactions
are mandatory. Presently, not enough is known about the details of the optical
potentials and nuclear response to isospin operators for many of the
projectile-target systems proposed for future DCE studies. Among these, the
20Ne + 76Ge DCE reaction is particularly relevant due to its connection with
76Ge double-beta decay. Purpose: We intend to characterize the initial-state
interaction for the 20Ne + 76Ge reactions at 306 MeV bombarding energy and
determine the optical potential and the role of the couplings between elastic
channel and inelastic transitions to the first low-lying excited states.
Methods: We determine the experimental elastic and inelastic scattering
cross-section angular distributions, compare the theoretical predictions by
adopting different models of optical potentials with the experimental data, and
evaluate the coupling effect through the comparison of the distorted-wave Born
approximation calculations with the coupled channels ones. Results: Optical
models fail to describe the elastic angular distribution above the grazing
angle (9.4{\deg}). A correction in the geometry to effectively account for
deformation of the involved nuclear systems improves the agreement up to about
14{\deg}. Coupled channels effects are crucial to obtain good agreement at
large angles in the elastic scattering cross section.
