期刊
OPTICS EXPRESS
卷 19, 期 9, 页码 8051-8065出版社
OPTICAL SOC AMER
DOI: 10.1364/OE.19.008051
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资金
- National Science Foundation [CBET-0747625]
- Harvard MRSEC [DMR-0820484]
- FAS Sciences Division Research Computing Group
- National Science Foundation under NSF [ECS-0335765]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [820484] Funding Source: National Science Foundation
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [0747625] Funding Source: National Science Foundation
We discuss a new method for simultaneously probing translational, rotational, and vibrational dynamics in dilute colloidal suspensions using digital holographic microscopy (DHM). We record digital holograms of clusters of 1-mu m-diameter colloidal spheres interacting through short-range attractions, and we fit the holograms to an exact model of the scattering from multiple spheres. The model, based on the T-matrix formulation, accounts for multiple scattering and near-field coupling. We also explicitly account for the non-asymptotic radial decay of the scattered fields, allowing us to accurately fit holograms recorded with the focal plane located as little as 15 mu m from the particle. Applying the fitting technique to a time-series of holograms of Brownian dimers allows simultaneous measurement of six dynamical modes - three translational, two rotational, and one vibrational - on timescales ranging from 10(-3) to 1 s. We measure the translational and rotational diffusion constants to a precision of 0.6%, and we use the vibrational data to measure the interaction potential between the spheres to a precision of similar to 50 nm in separation distance. Finally, we show that the fitting technique can be used to measure dynamics of clusters containing three or more spheres. (C) 2011 Optical Society of America
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