Single-detector 3D dynamic light scattering (3D DLS) emerges as a reliable technique to determine the drift velocity of out-of-equilibrium colloidal particles. In particular, our investigation reveals the appearance of oscillations of a well-defined frequency in the autocorrelation function of the scattered intensity when particles are immersed in a medium exposed to thermally induced convection. These oscillations arise as a consequence of the directed motion of particles due to the convection of the fluid. The experimental results obtained for different colloidal systems are corroborated by a theoretical model and thoroughly validated with fluid dynamics and Brownian dynamics simulations. The excellent agreement between experimental, theoretical and simulation data allows us to provide a solid and comprehensive explanation of the observed physical phenomena. This Letter, using an advanced dynamic light scattering technique, offers insights into the field of nonequilibrium particle dynamics, applicable not only to colloidal suspensions affected by steady-state diffusion-convection but also to other nonequilibrium scenarios, such as systems driven by external fields (e.g., gravitational, electric or magnetic fields).

中文翻译：

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通过单探测器 3D 动态光散射测量非平衡振荡的绝对速度


单探测器 3D 动态光散射 （3D DLS） 成为一种确定不平衡胶体颗粒漂移速度的可靠技术。特别是，我们的研究揭示了当粒子浸入暴露于热诱导对流的介质中时，散射强度的自相关函数中会出现明确频率的振荡。这些振荡是由于流体对流导致粒子的定向运动而产生的。针对不同胶体系统获得的实验结果由理论模型证实，并通过流体动力学和布朗动力学模拟进行了全面验证。实验、理论和模拟数据之间的完美一致性使我们能够对观察到的物理现象提供可靠而全面的解释。这封信使用先进的动态光散射技术，提供了对非平衡粒子动力学领域的见解，不仅适用于受稳态扩散对流影响的胶体悬浮液，也适用于其他非平衡场景，例如由外部场（例如，引力场、电场或磁场）驱动的系统。