Shaping nanoparticles and their optical spectra with photons

An experimental method to tailor the shape and the optical absorption spect ra of metallic nanoparticles is presented. It exploits the influence of las er irradiation on particle growth by self-assembly of atoms deposited on a substrate surface. By applying nanosecond light pulses of appropriate fluen ce and three different wavelengths, oblate silver particles with three fixe d axial ratios have been fabricated. Their optical extinction spectra were measured with s- and p-polarized light and are dominated by plasmon resonan ces at fixed photon energies determined by the axial ratio. Possible applic ations of such tailormade nanoclusters include catalytic converters and opt ical components with narrow-band extinction, the magnitude and center frequ ency of which can be specified in advance.