Ultrafast laser excitation can generate acoustic vibrations in metal nanostructures. Acoustic vibrations transfer energy in the particle to the environment via the emission of sound waves. The effect of the environment on the acoustic vibrations in nanostructures has been investigated and the studies show that the local environment has a very little effect on the vibrational periods. In contrast, the lifetimes of acoustic vibrations are considerably affected by the local environment. We investigate the damping of acoustic vibrations in Au nanowires suspended over the trenches in different liquid environments using transient absorption spectroscopy. The transient absorption measurements are repeated for the same nanowire before and after immersing into a liquid. This experimental configuration not only allows for a direct and quantitative determination of the effect of the surrounding liquid in the damping but also eliminates the uncertainties due to the substrate that typically arise when similar measurements are performed on supported nanostructures by providing a homogeneous environment around the nanowires. We observe a significant decrease in the lifetimes of acoustic vibrations after immersing the nanowires in a liquid whereas the frequencies of the vibrations remain almost unaffected. The observed damping of acoustic vibrations primarily comes from the acoustic impedance mismatch between the particle and its surrounding liquid.

Damping of acoustic vibrations in gold nanowires

255th National Meeting (2018)

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