Photoacoustic study of surface plasmons in metals

A photoacoustic technique was used to observe the nonradiative decay of surface plasmons in evaporated thin films of silver. The signal amplitudes from an attenuated total reflection photon–plasmon coupler were measured as a function of the angle of incidence and the chopping frequency of p-polarized 1.96-eV photons. A 1-D analysis was made on the photoacoustic data in conjunction with simultaneously measured absorptance data. Such an analysis allowed us to separate the nonradiative and the roughness-assisted radiative relaxations of the plasmons and determine their relative probabilities.