1 / 10

Light Scattering (pp. 53-63 in Shaw and pp. 193-244 in Hiemenz and Rajagopalan)

Light Scattering (pp. 53-63 in Shaw and pp. 193-244 in Hiemenz and Rajagopalan). Introduction Rayleigh Scattering Debye Scattering, Zimm Plots Dynamic Light Scattering. Introduction. Transmitted. Absorbed. Scattered. Turbidity. When there is no absorption.

wade-finch
Download Presentation

Light Scattering (pp. 53-63 in Shaw and pp. 193-244 in Hiemenz and Rajagopalan)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Light Scattering (pp. 53-63 in Shaw and pp. 193-244 in Hiemenz and Rajagopalan) • Introduction • Rayleigh Scattering • Debye Scattering, Zimm Plots • Dynamic Light Scattering

  2. Introduction Transmitted Absorbed Scattered Turbidity When there is no absorption • Information Obtained • Particle mass • non-perturbed • absolute determination • instantaneous • Particle size and shape • Dynamic information (diffusion constants)

  3. Rayleigh Scattering • particles small (< l/20, about 20-25 nm) • refractive index similar to medium • Debye Scattering • particles relatively large • refractive index similar to medium • Mie Scattering • few constraints on size or refractive index • easily applied only to spherical particles, • or particles where geometry is known (NOT discussed here)

  4. Experimental Apparatus

  5. Rayleigh Scattering Rayleigh found the following relationship for point scatterers (i.e. particle size < l/20): Why is the sky blue? (lred=700 nm, lblue=400 nm) Vertically vs. horizontally polarised light Insert Shaw Fig. 3.6

  6. Find an expression for a and replace in the Rayleigh equation... Assumptions • scatterers are isotropic,dielectric, • non-absorbing • n is not too large • size of scatterers is small cf. light wavelength

  7. Comparison to osmotic pressure • measurements: • Instantaneous, kinetics possible • covers a different particle size range Debye Scattering If particle size>l/20 we get interference effects... Use a correction factor P(Q)

  8. Correction term derived from X-ray scattering theory... Physical meaning of radius of gyration... n2 n1 r2 r3 n3 r1 centre of mass average radius swept out by a chain of n particles (e.g. polymer, protein…)

  9. Zimm Plots No interference effect, just like Rayleigh eqn. slope gives i.e. particle size info. particle MW info--Zimm plot c=0 Q=0 2B (+ Overheads)

  10. Dynamic effects

More Related