Abstract
We have discovered occurrence of strong narrow spectral lines in gold nanoparticles deposited on fluorine-doped tin oxide substrates at wavelengths 410, 440 and 550 nm under influence of 808 nm wavelength laser illumination with power about 200 mW. These lines appear just after the 1 s of illumination and are almost unchanged during all the remaining time of illumination. Such lines are absent for the other content of gold nanoparticles-modified substrates. So a principle role here is played by the inter-particle distances. The relaxation process is continued during 8-10 h and the samples return to their initial states. The occurrence of the such narrow spectral lines may be a consequence of the two-photon absorption related with the corresponding electron-phonon interactions due to specific interactions between the plasmons and the phonon subsystem and the free carriers.