Abstract

Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber υ = 10⁴ cm^-1 were obtained during the hydrolysis of FeCl₃ solutions. At first, the resulting turbid suspension of cigar-shaped β-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation ∝ υ⁴). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to υ^α, with α ≈ 2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension d_f roughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form υ^α with 1≤ α ≤ 4. While over limited spectral ranges α may be taken independent of υ , over wide ranges it decreases with increasing υ. This behavior is consistent with the theoretical limits of α = 4 at υ = 0, and α = 0 at υ = ∞. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is <i>Aυ</i>^α, with A and α fitted constants.

Turbidity of Monodisperse Suspensions of AgBr*

Chester R. Berry
J. Opt. Soc. Am. 52(8) 888-895 (1962)

The increase of the light transparency induced by a magnetic field for the colloid film based on α–FeOOH nanoparticles

Jian Li, Anrong Wang, Yueqiang Lin, Xiaodong Liu, Jun Fu, Lihua Lin, and Longlong Chen
Opt. Mater. Express 2(12) 1760-1767 (2012)

Particle sizing in strongly turbid suspensions with the one-beam cross-correlation dynamic light-scattering technique

Anthony J. Adorjan, James A. Lock, Thomas W. Taylor, Padetha Tin, William V. Meyer, and Anthony E. Smart
Appl. Opt. 38(15) 3409-3416 (1999)

Coherent reflection of light from a turbid suspension of particles in an internal-reflection configuration: Theory versus experiment

Augusto García-Valenzuela, Rubén G. Barrera, Celia Sánchez-Pérez, Alejandro Reyes-Coronado, and Eugenio R. Méndez
Opt. Express 13(18) 6723-6737 (2005)

Optical waveguiding in suspensions of dielectric particles

Richard S. Conroy, Brian T. Mayers, Dmitri V. Vezenov, Daniel B. Wolfe, Mara G. Prentiss, and George M. Whitesides
Appl. Opt. 44(36) 7853-7857 (2005)