In this study, the slip correction factor is assessed from the measurements of the electrical mobilities of PSL, SiO2 and Au nanoparticles under reduced pressure conditions. The asymptotic value (alpha+beta) of the slip correction factor, which is generally used for evaluating the particle drag force, are obtained for three different particle materials, and the values are used to assess the momentum accommodation function. Our experimental results show that the gas molecular slip is strongly dependent on the particle material characteristics. The higher the surface energy of the particle materials (PSL: 0.06 J/m(2), SiO2: 0.30 J/m(2), and Au: 8.78 J/m(2)), the more diffusive reflections observed in gas molecular collisions with nanoparticles (PSL: 87.3%, SiO2: 89.2%, and Au: 99.6%). (c) 2013 Elsevier Ltd. All rights reserved.