Re-evaluation of the slip correction parameter of certified PSL spheres using a nanometer differential mobility analyzer (NDMA)

The slip correction parameter measured by Kim et al. (2005) is re-evaluated with the newly issued current smallest standard reference material SRM^® 1964 (PSL 60.39nm). The same experimental method utilizing the electrical mobility technique under low pressure condition is used. From the measured peak voltages at low pressures down to 8.63kPa (Kn=81), slip correction factor (C) is calculated, and then the slip correction parameter (A) is obtained by nonlinear curve fitting. The parameter A is 1.165+0.480exp(-1.001/Kn) with the asymptotic value of 1.645 for the free molecular regime, which corresponds to a diffuse reflection fraction of 0.873. The value of A is at most 0.1% different from the value reported by Kim et al. (2005) 1.165+0.483exp(-0.997/Kn) and the uncertainty is reduced by about 0.5% to a value of about 1.5%.