Time-resolved laser scattering spectroscopy of a single metallic nanoparticle

A new technique is proposed for the transient absorption spectroscopy of a single metallic nanoparticle. This technique is based on a differential interference contrast (DIC) microscopy using pulsed laser light. A single nanoparticle is excited by a pumping laser beam, and the DIC signal of a probing light is measured to precisely determine the amplitude and phase of the forward-scattered light. The refractive index and the absorption coefficient of the excited particle can be estimated on the basis of the Rayleigh scattering theory. By changing the delay time between the pumping and probing pulses, absorption dynamics of a single nanoparticle can be observed on a femtosecond time scale. As a preliminary experiment, the electron dynamics of a 70 nm silver colloidal particle was analyzed with this technique.