SYSTEMATIC STUDY OF (NA-N)(2) DIMER TRANSIENT STATE IN NA-N+NA-N COLLISIONS (N=8, 9, 19, AND 20)

From distance dependent tight-binding molecular dynamics simulations, we systematically study the Na-n + Na-n collision dynamics around the first two closed shells (n = 8 and 20). We investigate the stability of sodium cluster dimers (Na-n)(2), for many events with random relative orientation at finite temperature, various impact parameters and incident energies. We find that (Na-8)(2), (Na-9)(2), (Na-19)(2) and (Na(2)0)(2) can exist during about 3000 fs in central collisions while they can exist up to about ten thousands fs in peripheral collisions with larger impact parameters in fusion mechanism at c.o.m energy per atom E(cm)/n = 0.025 eV. We observe that the lower the incident energy, the longer the lifetime of the cluster dimers in both central and peripheral collisions. There is no apparent difference in the dynamical stability of (Na-8)(2) and (Na-9)(2), (Na-19)(2) and (Na-20)(2) although (Na-8)2 and (Na-20)(2) are respectively slightly colder than (Na-9)(2) and (Na-19)2 for the same incident energy per atom and the same impact parameter.