Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

he yield ratios of neutron-proton (R(n/p)) and ³H-³He (R(³H/³He)) with reduced rapidity from 0 to 0.5 were simulated for 50 MeV/u even-even ^36-56Ca + ⁴⁰Ca, even-even ^48-78Ni + ⁵⁸Ni and ^100-139Sn (every third isotopes) + ¹¹²Sn at full reduced impact parameters using the isospin-dependent quantum molecular dynamics (IQMD) model. The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model, which was used for the phase space initialization of the projectile and target in IQMD. We defined the unified neutron skin thickness as ΔR_np=2>_n^1/2-2>_p^1/2, which was negative for neutron-deficient nuclei. The unified ΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal, except for extreme neutron-rich isotopes, which is a type of scaling behavior. The yield ratios of the three isotopic chains-induced reactions, which dependent on the reduced impact parameter and the unified neutron skin thickness, were studied. The results show that both R(n/p) and R(³H/³He) decreased with a reduced impact parameter for extreme neutron-deficient isotopes; however, they increased with reduced impact parameters for extreme neutron-rich isotopes, and increased with the ΔRnp of the projectiles for all reduced impact parameters. In addition, a scaling phenomena was observed between ΔRnp and the yield ratios in peripheral collisions from different isotopic chain projectiles (except for extreme neutron-rich isotopes). Thus, R(n/p) and R(³H/³He) from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.