  Heavy-ion collisions are a good tool to explore hot nuclear matter below
saturation density. It has been established that if a nuclear system reaches
the thermal and chemical equilibrium, this leads to scaling properties in the
isotope production when comparing two systems which differ in proton fraction.
This article presents a study of the isoscaling properties of an expanding gas
source exploring different thermodynamic states (density, temperature, proton
fraction). This experimental work highlights the existence of an isoscaling
relationship for hydrogen and 3He, 4He helium isotopes which agrees with the
hypothesis of thermal and chemical equilibrium. Moreover, this work reveals the
limitations of isoscaling when the two systems differ slightly in total mass
and temperature. Also, a discrepancy has been observed for the 6He isotope,
which could be explained by finite size effects or by the specific halo nature
of this cluster.
