Figure 4. Laser power and particle size dependence of the contact potential.

Contact potential U₀ as a function of the laser power P for particles of different size 2R=2, 3 and 4 μm. U₀ including its error has been obtained by extrapolating the experimental data depicted in Fig. 3. From a linear fit (dashed lines) we estimate the normalized contact potential U₀/P for the respective particle sizes. The inset shows the dependence of U₀/P on the particle diameter 2R and the dotted line is a linear fit to the data U₀/P∼0.17 k_BT W⁻¹ × (2R μm⁻¹).