摘要
Under 2keV Xe ion bombardment of a ^(63)Cu69.1^(65)Cu30.9 isotope mixture,isotope fractionation difference between small and large polar emission angles,δ(15°)-δ(75°),was calculated by use of a dynamic Monte Carlo program.Calculation results show that δ(15°)-δ(75°) is large at both the zero fluence and the high fluence,then it minimizes at a low fluence of 1.6x 10^(15) ions/cm^(2) between two fluence limits.An important cause of this minimum is that the surface composition gradient of ^(63)Cu maximiles at the fluence of 1.6x10^(15) ions /cm^(2).
