However, a better agreement between theory and experiment
is found if the absorbance ratios are determined in the wavelength
region below 600 nm. Figure 6b shows the ratio of the absorbance
at the surface plasma resonance peak (Aspr) to the absorbance at
450 nm (A450) in dependence of the logarithm of the particle
diameter in the size range from 5 to 80 nm. The theoretical data
(circles) exhibit an excellent linearity (solid line in Figure 6b; R2
> 0.999), and hence the ratio Aspr/A450 should be particularly
suitable to calculate the particle diameter (in nanometers) from