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Acoustic Vibrations of Al Nanocrystals: Size, Shape, and Crystallinity Revealed by Single-Particle Transient Extinction Spectroscopy
摘要： Acoustic vibrations in plasmonic nanoparticles, monitored by an all-optical means, have attracted significant increasing interest because they provide unique insight into the mechanical properties of these metallic nanostructures. Al nanostructures are a recently emerging alternative to noble metal nanoparticles, because their broad wavelength tunability and high natural abundance make them ideal for many potential applications. Here we investigate the acoustic vibrations of individual Al nanocrystals using a combination of electron microscopy and single-particle transient extinction spectroscopy, made possible with a low-pulse energy, high sensitivity, and probe-wavelength-tunable, single-particle transient extinction microscope. For chemically synthesized, faceted Al nanocrystals, the observed vibration frequency scales with the inverse particle diameter. In contrast, triangularly-shaped Al nanocrystals support two distinct frequencies, corresponding to their in- and out-of-plane breathing modes. Unlike ensemble measurements, which measure average properties, measuring the damping time of the acoustic vibrations for individual particles enables us to investigate variations of the quality factor on the particle-to-particle level. Surprisingly, we find a large variation in quality factors even for nanocrystals of similar size and shape. This observed heterogeneity appears to result from substantially varying degrees of nanoparticle crystallinity even for chemically synthesized nanocrystals.
关键词： quality factor,Al nanocrystals,single-particle transient extinction spectroscopy,acoustic vibrations,nanoparticle crystallinity
更新于2025-09-23 15:19:57
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Improving the effects of laser hardening of steels by applying a longitudinally torsional ultrasonic field
摘要： The paper is devoted to the expediency of using ultrasonic treatment in combination with laser hardening for U8, U10, X12M steels and the study of the effect of ultrasonic longitudinal and torsional acoustic vibrations on the intensification of an increase in the concentration of point defects in the crystal structure. The introduction of a longitudinal and torsional ultrasonic field by transforming longitudinal ultrasonic vibrations made it possible to form a highly concentrated effect, which led to an increase in the effects of laser hardening.
关键词： ultrasonic treatment,crystal structure,steels,laser hardening,longitudinal and torsional acoustic vibrations
更新于2025-09-16 10:30:52
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Stimulated Raman Scattering at Induced Acoustic Vibrations of Elastic Particles in Suspensions Placed in an Optical Cavity
摘要： The stimulated low-frequency Raman scattering at acoustic vibrations of elastic inclusions in a liquid heterogeneous medium placed in an external open optical cavity has been investigated. The amplitudes of stationary ?eld oscillations in the cavity at the frequencies of the excitation and the ?rst Stokes component are found within a two-dimensional model. The speci?c features of the oscillation in dependence of the parameters of the cavity and Raman-active medium have been studied based on the simulation results.
关键词： liquid heterogeneous medium,acoustic vibrations,elastic particles,optical cavity,stimulated Raman scattering
更新于2025-09-04 15:30:14