  The possible occurence of highly deformed configurations is investigated in
the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si +
$^{12}$C and $^{28}$Si + $^{28}$Si reactions, respectively, by using the
properties of emitted light charged particles. Inclusive as well as exclusive
data of the heavy fragments (A $\geq$ 6) and their associated light charged
particles (p, d, t, and $\alpha$-particles) have been collected at the IReS
Strasbourg VIVITRON Tandem facility with two bombarding energies
$E_{lab}(^{28}$Si) = 112 and 180 MeV by using the ICARE charged particle
multidetector array, which consists of nearly 40 telescopes. The measured
energy spectra, velocity distributions, in-plane and out-of-plane angular
correlations are analysed by Monte Carlo CASCADE statistical-model calculations
using a consistent set of parameters with spin-dependent level densities.
Although significant deformation effects at high spin are needed, the remaining
disagreement observed in the $^{28}$Si + $^{12}$C reaction for the S
evaporation residue suggests an unexpected large unstable $^{8}$Be cluster
emission of a binary nature.
