Investigation of the ultrafast dephasing time of gold nanoparticles using incoherent light

Measurement of the phase relaxation time and nonlinear susceptibility of gold nanoparticles is demonstrated, using incoherent light. The diameters of the gold particles ranged from 50 to 400 Å. Experiments were performed in the vicinity of the surface plasmon resonance frequency and the resonantly enhanced susceptibility was found to be approximately 10−16 m2 V−2. The dephasing time was determined to be of the order of, or faster than, 20 fs.