Abstract

The conduction electrons of metallic nanoparticles (NPs) exhibit collective oscillations named localized surface plasmon (LSP) that needs to be well understood aiming at various photonic applications [1]. In particular the study of the dephasing relaxation time, T₂, of the LSP is important because the local electromagnetic field enhancement in the vicinity of the NPs is proportional to T₂, which depends on the metal element, size and shape of the NPs, chemical enviroment, and the frequency of the excitation radiation [2]. For colloidal NPs it is expected a dependence of T₂ on the stabilizing agents of the colloid but this effect is often underlooked because T₂ ≤ 10 fs being difficult to measure using time-resolved techniques [3]. Besides this, the chemical synthesis methods commonly used produce NPs with different sizes and shapes, giving rise to inhomogeneously broadened optical extinction profiles. Several frequency-resolved techniques have been proposed to measure T₂ [4] but no systematic study is available concerning the effect of the NPs’ capping agents.

© 2011 Optical Society of America