slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Inelastic Scattering PowerPoint Presentation
Download Presentation
Inelastic Scattering

Loading in 2 Seconds...

play fullscreen
1 / 31

Inelastic Scattering - PowerPoint PPT Presentation


  • 312 Views
  • Uploaded on

Inelastic Scattering. Raman. Compton. Acoustic Mode Scattering. Bragg and Brillouin. Why the sky is blue?. Rayleigh Scattering.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Inelastic Scattering' - RexAlvis


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide4

Acoustic Mode Scattering

Bragg and Brillouin

slide6

Rayleigh Scattering

Rayleigh scattering refers to the scattering of light off of the molecules of the air, and can be extended to scattering from particles up to about a tenth of the wavelength of the light.

slide7

Mie Scattering

The scattering from molecules and very tiny particles (< 1 /10 wavelength) is predominantly Rayleigh scattering. For particle sizes larger than a wavelength, Mie scattering predominates.

slide8

Mie scattering is not strongly wavelength dependent and produces the almost white glare around the sun when a lot of particulate material is present in the air. It also gives us the the white light from mist and fog.

slide9

SAXS/WAXS

WAXS

DLS

SLS

SALS

Photons

Rayleigh Scattering

Neutrons

SANS

SPIN-ECHO

slide10

ESRF- EUROPEAN SYNCHROTRON RADIATION FACILITIES

X-RAYS SOURCE

ILL : INSTITUT LAUE LANGEVIN

NEUTRONS SOURCE

ESRF RING

ILL

REACTOR

GRENOBLE, FRANCE

slide11

Elastic and Quasi-Elastic Light Scattering

Elastic: Mw, Rg, A2 , form factor P(q), Persistence Length, etc.

Dynamic: relaxation times, Diffusion Coefficients, Mobilities, etc.

slide12

SAXS/WAXS

X-Ray Scattering

2-D detector

up to 600 Å

resolution

Nano-Structures: x-rays Scattering

Form factor, Anisotropy, Polyelectrolytes, Nano-materials : Copolymers, Colloids, Micelles, Polymer Liquid Crystals, etc.

slide13

2

1.5

1

0.5

0

0

0.05

0.1

0.15

0.2

Intensity vs wavevector q

Elastic Scattering

Size and Shape

Mw (Molecular Weight

Rg (Radius of Gyration)

A2 (Virial Coefficient)

o-1

q(A

)

Light scattering, SANS, SAXS

Dynamic Scattering: Diffusion Coefficient D or

Hydrodynamic Radius Rh

slide15

SALT-FREE POLYELECTROLYTE CHAINS (Electrostatic Forces)

4

3.5

3

2.5

D=2p/q*

I(q)

2

1.5

1

D=2p/q*

0.5

Dilute : q*~c 1/3

0

0

0.05

0.1

0.15

0.2

Uniform or Cubic distribution

Semi-dilute : q*~c 1/2

Parallel Arrangement

SAXS

REPULSION

Scattering Peak !

Expansion of the Chain

q*

o-1

q(A

)

slide16

(1/3) : Uniform / Cubic Arrangement

(1/2) : Cylindrical 2-D Arrangement

slide17

Variation of qmax as a Function

of Xanthan Concentration

Xanthan “Salt-Free” Solutions

-1

10

-2

10

-3

10

-4

10

-6

-5

-4

-3

-2

-1

10

10

10

10

10

10

XANTHAN/LS/SAXS

q-SAXS Range

)

°-1

(A

max

q

0.497

q

=0.34*C

max

q-Light Scattering Range

3

C (g/cm

)

E. Sadlik, M. Villetti, M. de Souza, V. Soldi and R. Borsali (in preparation )

slide18

Sample [Solutions, Gels, Melts ]

Polarizer

Beam Stop

(Polymers,

Colloïds, etc.)

Laser

l

Q

Pinhole

Lens

Scattering Angle

Analyzer

Pinhole

q=(4p/l)n sin(Q/2)

Lens

Wavevector

Detection

(Optical Fiber)

Computer

Dynamic

I(q,t)

Correlator

Static

Photons Count

<I(q)>

LIGHT SCATTERING - EXPERIMENTAL SET UP

slide20

Quasi-Elastic Light Scattering or...

SLS - Static Light Scattering

The amount of light scattered is directly proportional to the product of the weight-average molar mass and the macromolecule (solute) concentration, i.e.,

LS ~ Mw·c

  • R(Q) is the excess intensity of scattered light at angle Q
  • c is the sample concentration
  • Mw is the weight-average molecular weight (molar mass)
  • A2 is a second viral coefficient
  • K* is an optical parameter equal to
  • 4p2n2 (dn/dc)2 / (lo4NA)
  • n is the solvent refractive index and dn/dc is the refractive index increment
  • NA is Avogadro’s number
  • lo is the wavelength of the scattered light in vacuum.

Based on Zimm’s formalism, the Rayleigh-Debye-Gans light scattering model for dilute polymer solutions can be expressed as equation below:

slide21

The function P(Q) describes the angular dependence of scattered light.

The expansion of 1/ P(Q) to first order gives:

1/ P(Q) = 1 + (16p2/3l2) <rg2>. sin2(Q/2) + f4 sin4(Q/2) +...

At low angles the angular dependence of light scattering depends only on the mean square radius <rg2> (alternatively called radius of gyration) and is independent of molecular conformation or branching.

Zimm plot

A plot of K*c /R(Q) vs. sin2(Q/2) yields a curve whose

intercept gives Mw and whose slope at low angles gives <rg2>.

slide22

ZIMM DIAGRAM

KC/I(q) = (1/Mw)(1+q2Rg2/3) + 2A2C

KC/I(q)

C->0

KC/I(q) = (1/M) (q ->0 ; C ->0)

KC/I(q) = (1/M)(1+q2Rg2/3) ; (C ->0)

b -> Slope = Rg2/3M

b

q->0

KC/I = (1/Mw)+ 2A2C ; (q->0)

a

a -> Slope = 2A2

C2

C1

C4

C3

(1/M)

q2+k’C

Measure of I(q) as a function of Concentration

and Scattering Angle allows the determination of:

The Molecular Weight : Mw

The Radius of Gyration : Rg

The Second Virial Coefficient : A2

& The Form Factor : P(q)

slide25

O coeficiente viral A2

[HA]=0.1mg/mL

[PVP]=30mM [SDS]=7mM

slide26

Photon Correlation Spectroscopy or...

DLS - Dynamic Light Scattering

slide28

Solvent

Polymer solution

slide29

DYNAMIC LIGHT SCATTERING

Linear & Cyclic PS-PI in heptane