SINGLE-PARAMETER EXPRESSION FOR IONS REFLECTION FROM SURFACES

Based on a detailed analysis of the Boltzmann equation for ion transpo rt in solids, it has been shown that for low-energy ions incident on a heavy element target the distribution function of the ions can be det ermined by one single parameter, called the scaled transport cross-sec tion, which was defined earlier [1]. This means that the transport qua ntities of different ion-target-energy combinations should be similar only when their scaled transport cross-section is the same. To test th is significant conclusion, we undertook a set of systematic and extens ive calculations of reflection coefficients using the improved biparti tion model of ion transport. The systematic calculations include 3410 ion-target-energy combinations, namely H, D, T, He, Li, B, C, N, O, Ne ions with energy ranges from 10 eV to 1 MeV normally incident to C, A l, Cu, Mo, Ag, W, Au, Pb, U targets. The only restrictions is M(1)/M(2 ) < 1/6. The calculations verify that particle and energy reflection c oefficients present an excellent one-to-one correspondence to the scal ed transport cross-section. Furthermore, based on the calculations, un iversal expressions for both particle reflection coefficients and ener gy reflection coefficients for normal ion incidence have been obtained by fitting the numerical data. By comparing the results calculated by the universal expressions with experimental and Monte Carlo data, it is shown that the expression can describe reflection coefficients well .