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Small Angle Scatteringof neutrons and x-rays
Volker UrbanVolker UrbanOak Ridge National Laboratory
National School on Neutron and X-ray ScatteringMay 30 – June 13, 2009
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I am scattering like light…Suzanne Vega – Small Blue Thing
Outline
• Applications – is SAS for you? • Applications – is SAS for you? • Comparison with microscopy and diffraction
B i t f th t h i• Basic concepts of the technique• At the beamline – SAS jargon• Planning a SAS experiment and data reduction• Break• SAS data analysis and interpretation
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SAS of x-rays, neutrons, laser light
• SAXS & SANS: structural information 1nm-1μmX rays• X-rays– Rotating anode / sealed tube: ~ 400 k$– Synchrotron: high flux, very small beams
• Neutrons– Isotope contrast, high penetration, magnetic contrast
L Li ht tt i• Laser Light scattering– Bench top technique, static and dynamic
• Applications in … Applications in … – Important for polymers, soft materials, (biology)– Particulate and non-particulate
Pretty much anything 1nm-1μm …really
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– Pretty much anything 1nm-1μmanything?
SAS applications A to ZAlzheimer’s disease, aerogel, alloys Magnetic flux lines,
But what about SEM, TEM AFM
Alzheimer s disease, aerogel, alloys
Bio-macromolecular assemblies, bone
Colloids, complex fluids, catalysts
g ,materials science
Nano-anything
Orientational order
TEM, AFM …?
Detergents, dairy (casein micelles)
Earth science, emulsions
f
Orientational order
Polymers, phase behavior, porosity
Quantum dots (GISAXS)Fluid adsorption in nanopores, fuel cells,
food science (chocolate)
Gelation, green solvents
( )
Rubber, ribosome
Soft matter, surfactants, switchgrass
High pressure, high temperature…, hydrogen storage, helium bubble growth in fusion reactors
Time-resolved, thermodynamics
Uranium separation
V i l i Implants (UHDPE)
Jelly
Kinetics (e g of polymerization or protein
Vesicles, virus
Wine science
Xylose isomeraseKinetics (e.g. of polymerization or protein folding), keratin
Liquid Crystals
Xylose isomerase
Yttrium-stabilized zirconia (YSZ)
Zeolites
SANS vs. Synchrotron SAXS
• SAXS & SANS– nm scale structural analysis (~1nm-1μm)– Non-destructiveNon destructive– In-situ
• Synchrotron X-raysHigh throughput– High throughput
– Time-resolution (ms – ps)– Tiny beams – microfocus: e.g. scanning of cells
Neutrons• Neutrons– ‘see’ light atoms: polymers, biology, soft condensed matter, hydrogen in metals– Isotope labeling
High penetration– High penetration• bulky specimens, e.g. residual stress in motor block• complicated environments (P,T), e.g. 4He cryostat
– Magnetic contrast
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Magnetic contrast
Neutron Scattering and Microscopy
• Common features– Size range 1nm-1μmg μ– Contrast labeling options (stains / isotope labels)
• SAS practical aspectsN i l l ti h i t – No special sample preparation such as cryo-microtome
– Sample environments control (p, T, H)– Non-destructive (exception: radiation damage in synchrotron beam)– In-situ, time-resolved
• Fundamental difference– “Real space” image with certain resolutionReal space image with certain resolution– Scattering pattern, averaged over volume
• Complimentarity
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Alzheimer’s Disease – β-Amyloid
• Among leading causes of death
• Miss-folded peptides form hierarchical ordered fibril structures & plaques
• Structure established using synthetic model peptides and complimentarymethods NMR, SANS, EM
• NMR− β-fold
• SANS − Fiber shape− Diameter− 6 sheet stack
• EM − Overall
morphologyp gy− Twist
T.S. Burkoth et al. J. Am. Chem. Soc. 2000, 122, 7883-788930 nm
Microscopy : enlarged image
incidentbeam
SampleImage
f i iSample focusing optics
SAS : interference patterny
φ
x
φincident
beam
θ
DetectorSample
beam
Scattering and Diffraction (Crystallography)( y g p y)
• Strictly/historical: Scattering from individual electrons/nuclei, Diffraction through interference of primary wavesDiffraction through interference of primary waves
• Today’s common language: Diffraction from crystals, Scattering from anything else (less ordered) > the difference g y g ( )is in the SAMPLE!
• Same basic physics: interactions of radiation with matter– SAXS/WAXS, SAND/WAND – Instruments: resolution (D) / flux (S)– Diffraction needs crystals, scattering does not.act o eeds c ysta s, scatte g does ot– Analysis?!
• At small Q (small angles, large λ): observe “blobs” NOT S
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atoms – allows SLD contrast variation!
Diffraction (Crystallography)here at Small Anglesg
Shear ordered charge gstabilized colloidal dispersion
Scattering along Bragg-rodsof layered system > stacking sequence
Pl t G t V ld U i A hPlate Geometry - Versmold, Uni Aachen
Diffraction - Bragg’s Law
W ith l th λ fl t d b t f l tti lWaves with wavelength λ are reflected by sets of lattice planes
θ θ
d θ θ
2θ = ϑ
Δ = 2d sin(θ)Phase shift = 2π Δ/λ
1/d = 2/λ sin(ϑ/2)if Δ = n λ then reflection otherwise extinction nλ = 2d sin(θ)
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Scattering Vector – q aka momentum transfer, Q, h, k, s
Wave vector k: |k| = k = 2π/λWave vector k: |k| k 2π/λ
ko
k ⎟⎠⎞
⎜⎝⎛=
2sin21 ϑλdo
kq
⎠⎝ 2λd
2ko
ϑ
qd π2
=
⎟⎠⎞
⎜⎝⎛=⎟
⎠⎞
⎜⎝⎛=
2sin4
2sin2 ϑϑ
λπkq q in nm-1 or Å-1
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Neutron Scattering Intensity
• Incoming waves scatter off individual nuclei according to scattering length b (can be + or -).scattering length b (can be or ).
• Interference of wavelets from distribution of nuclei (= structure) adds up to “net scattering” amplitude (Fourier t f f t t )transform of structure).
• Measured intensity is the magnitude square of amplitude.• Measured intensity is also the Fourier transform of pair
correlation function P(r).
2
3))(()( ∫ •−−= rqis rderqI
rrr ρρ
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V
Absolute Intensity / Scattering Cross Section cm 1 ?Section – cm-1 ?
dI
Io
dIdΩD
ΩΣ
=Ω d
dDTIddI
o Ω=
ΩΣ
ddI
DTIdd 1
[cm-1sterad-1]ΩΩ dd
dI/dΩ = Scattered intensity per solid angleIo = Primary beam intensity
ΩΩ dDTId o
T = Transmission (x-ray absorption, incoherent neutron scattering)D = ThicknessdΣ/dΩ = Scattering cross section per unit volume [cm-1sterad-1]
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Contrast – Atomic Scattering Lengths
Element Neutrons X-rays Electrons
Contrast Atomic Scattering Lengths
(10-12 cm) (10-12 cm)
1H -0.374 0.28 1
2H (D) 0.667 0.28 1
C 0 665 1 67 6C 0.665 1.67 6
N 0.940 1.97 7
O 0 580 2 25 8O 0.580 2.25 8
P 0.520 4.23 15
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SANS – Contrast Variation
Bile salt micelle
9.0
4 05.06.07.08.0
ngth
den
sity
10-
14cm
.Å-3
DNA
D-protein
D-DNA
D2O/H2O Bile salt micelle
0.01.02.03.04.0
scat
terin
g le
n
water
proteinRNA
Phosphat Ch
contrast variation
Bil lt i ll-1.00 10 20 30 40 50 60 70 80 90 100
%D2O
Bile salt micelle
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Rubber (Polymer Network)
• Unique mechanical properties – “liquid” on local scale but long range structure memory
• Economic importance – Tires• Economic importance – Tires
??• Blend “normal” H- and some
% D-polyisopreneCross link to form r bber net ork• Cross-link to form rubber network
• Stretch rubber sample in the SANS beam and collect data
1.5
SANS of labeled stretched rubber
NIST NG7 data
small q larger q• Stronger anisotropy at smaller q (larger distances)
2.0
smaller q (larger distances)• Ellipse > diamond transition at large deformation• Warner-Edwards tube approach:
⎧affinely deformed Gauss chain
2.6
12
0 0
( , ) 2 exp ( ) ( )x
S q N dx dx Q x xμ μμ
λ λ
⎧⎪⎪′ ′= − −⎨⎪⎪⎩
∏∫ ∫r
2 9
22 2
22
( )(1 ) 1 exp2 6d x xQ
dRμ
μ μλ
⎪⎩⎫⎛ ⎞⎡ ⎤⎪⎜ ⎟⎢ ⎥
′− ⎪⎜ ⎟⎢ ⎥− − − ⎬⎜ ⎟⎢ ⎥⎪
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2.9
qmax ~ 0.009 Å
22
2
2 62 6
g
g
dRR
μ μμ
⎜ ⎟⎢ ⎥⎪⎜ ⎟⎢ ⎥⎪⎜ ⎟⎢ ⎥⎣ ⎦⎝ ⎠⎭
non-affine fluctuation contribution
1.5
SANS at increasing deformation
NIST NG7 data
small q larger q• Self-consistent tube model
2.0
with deformation dependent tube width:
2.6
2 9
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2.9
qmax ~ 0.009 Å
E. Straube et al., Macromolecules 27, 7681 (1994)E. Straube et al., Physical Review Letters 74, 4464 (1995)
At the beamline
Monochromatic y
Monochromatic beam (Δλ/λ) Pinhole camera (Δθ/θ)
A d t tincident θ
φ
Area detectorbeam
Sample Detector
x
Sample Detector
I(ϑ)
%D2O r6398 0 r6412 3 r6418 6 r6424 8
If data isotropic:azimuthal average I(ϑ)(aka “radial average”)
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ϑ( g )
Monochromator – Velocity Selector
10cm(MDR-13, Mirrotron, Hungary)
Cold Thermal
mvh
phλ ==
Cold ThermalT (K) 20 300v (m/s) 574 2224E (meV) 1.7 25.9
Å
De Broglie:
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mvpλ (Å) 6.89 1.78
SANS Instrument – a pinhole camera?
pinhole So it does take pictures?
object Yes, but of what?
Of thOf the source aperture, not of the sample!
imagep
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Layout of a SANS instrument
“pinhole”
up to 80m, D11 ILL
Typical layout at a continuous (reactor) source
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SANS at a pulsed source
EQ-SANS, SNS
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SAXS at synchrotrons
ESRF ID-2 High Brilliance B liBeamline
SAXS, WAXS, USAXS, ASAXS
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SANS guide hall (HFIR)SANS guide hall (HFIR)
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SANS guide hall (HFIR)
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Practical Considerations at SANS and SAXS User Facilities
• Thou shalt plan well thy experiment!• What Q-range would I like, and what must I have?• For how long should I measure my samples? – counting
statistics• How will I correct for backgrounds?• How can I optimize my sample quality?• Less is often more: Do fewer things but those do right! g g
(especially with neutrons) • Ask your local contact / instrument scientist for advice
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ywell ahead of time!
Data Reduction, Processing, Correction
• Normalization to monitor or time• Backgrounds• Transmission• Azimuthal averaging• Absolute intensity scale (cm-1) Absolute intensity scale (cm )
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Break
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Analysis of SAS datahere typical particulate solution scattering
• Δρ2 - Contrast = square of scattering length density diff b t ti l d = Δρ2 n V2 P(q) S(q))(q
ddΩΣ
difference between particle and medium– x-rays: electron density
Δρ n V P(q) S(q))(qdΩ
lim q,n → 0:
– neutrons: isotope labeling, particularly H > D
P( ) Si & h
= Δρ2 n V2)0( =ΩΣ qdd
• P(q) - Size & shape• S(q) - Interaction
• n - Number density (concentration) V P ti l l• V - Particle volume (molecular mass)
Measure and subtract background very carefully!Measure and subtract background very carefully!Do the absolute calibration – it’s worth the effort!
Alzheimer’s Disease – β-Amyloid
• Among leading causes of death
• Miss-folded peptides form hierarchical ordered fibril structures & plaques
• Structure established using synthetic model peptides and complimentary methods NMR, SANS, EM
• NMR− β-fold
• SANS − Fiber− Diameter− 6 sheet stack
• EM − Overall
morphologyp gy− Twist
T.S. Burkoth et al. J. Am. Chem. Soc. 2000, 122, 7883-788930 nm
Analysis of SAS data
S(q) * P(q) is not always a useful approach!
• P(q)– Guinier approximation → radius of gyration: Rgg
(modified Guinier for rods and sheets)f f /
ggg RRqRRqqI3522 :sphere;13/)](ln[ =<∝
– Form factor fit / modelingsphere, ellipsoid, rod, protein structure, fractal etc.
• S(q)• S(q)– hard sphere potential, sticky sphere etc.
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SAS Analysis –A spacewalk of sortsFourier Q reciprocal space
Carl Meade and Mark Lee rehearse spacewalk contingency plans in 1994
Fourier, Q, reciprocal space
36 Managed by UT-Battellefor the U.S. Department of Energy Presentation_nameEd White, the first American to walk in space, hangs out during the Gemini 4
mission. He's attached to the craft by both umbilical and tether lines.Bruce McCandless II took the first untethered space walk in February 1984. Here we see him from Challenger, floating above Earth.
Sphereprecisely: monodisperse sphere of uniform d it ith h d th fdensity with sharp and smooth surface
1.0
0.8
0.6
P(Q
)
0.4
0 2
100 Åradius
0.2
0.00 40 30 20 10 0
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0.40.30.20.10.0
Q (Å-1)
Sphere1.0
0.8
0 60.6
0.4
P(Q
)
0.2
0.0 2 3 4 5 6 7 8 90.01
2 3 4 5 6 7 8 90.1
2 3 4
Å 1 10-1
100
Q (Å-1)
-4
10-3
10-2
10
Q)
10-6
10-5
10 4
P(Q
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10-8
10-7
0.40.30.20.10.0
Q (Å-1)
Sphereprecisely: monodisperse sphere of uniform d it ith h d th f
100
density with sharp and smooth surface
10-2
10-1
Q-4
10-4
10-3
P(Q
)
10-6
10-5
P
10-8
10-7
2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 5 6 7
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0.0012 3 4 5 6 7
0.012 3 4 5 6 7
0.12 3 4 5 6 7
1Q (Å-1)
Sphere + constant background
10-1
100
4
68
1
10-3
10-2
10
80.1
2
4
-5
10-4
10 3
P(Q
)
2
4
68
P(Q
)
7
10-6
10-5
4
68
0.01
10-8
10-7
2 3 4 5 6 7 8 90.01
2 3 4 5 6 7 8 90.1
2 3 4
1
0.001
2
0.0012 3 4 5 6 7
0.012 3 4 5 6 7
0.12 3 4 5 6 7
11
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Q (Å-1)Q (Å-1)
Spheres of different sizes
10
1
0.1
P(Q
)
0.01
0.0010 001
2 3 4 5 6 7 80 01
2 3 4 5 6 7 80 1
2 3 4
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0.001 0.01 0.1Q (Å-1)
Ellipsoid aspect ratio 1.2
10-1
100
-3
10-2
10
5
10-4
10 3
P(Q
)
10-6
10-5
10-8
10-7
2 3 4 5 6 7 8 90.01
2 3 4 5 6 7 8 90.1
2 3 4
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Q (Å-1)Rg same as sphere for following objects
Ellipsoidaspect ratio 1.5
1
100
10-2
10-1
10-4
10-3
P(Q
)
10-6
10-5
10-8
10-7
0 0012 3 4 5 6 7 8
0 012 3 4 5 6 7 8
0 12 3 4
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0.001 0.01 0.1Q (Å-1)
Circular Cylinderwith same Rg as the sphere
68
11.0
0 1
2
4
6
0.8
2
4
68
0.1
P(Q
)
0.6
P(Q
)
4
68
0.01
20.4
0 2
0.001
2
4
2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4
0.2
0.0 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 3 4
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0.001 0.01 0.1Q (Å-1)
0.001 0.01 0.1Q (Å-1)
“Long & thin” cylinder
68
1
2
4
6
Q-1
4
68
0.1
P(Q
)
4
68
0.01
2P
0.001
2
4
2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 3 4
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0.0012 3 4 5 6 7 8
0.012 3 4 5 6 7 8
0.12 3 4
Q (Å-1)
Disk
4
68
1
80.1
2
4
Q-2
2
4
68
P(Q
)
4
68
0.01
0.001
2
0.0012 3 4 5 6 7 8
0.012 3 4 5 6 7 8
0.12 3 4
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Q (Å-1)
Polymer coil
68
1
0.1
2
4
Q-2
2
4
68
0.1
P(Q
)
4
68
0.01
0.001
2
0 0012 3 4 5 6 7 8
0 012 3 4 5 6 7 8
0 12 3 4
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0.001 0.01 0.1Q (Å-1)
Guinier Analysis size of any kind of object
• At small Q anything that could reasonably be considered an object follows Guinier approximationobject follows Guinier approximation.
ggg RRqRRqqI3522 :sphere;13/)](ln[ =<∝
• Modified Guinier approximations exist to determine cross ti l di f d thi k f h t
ggg 3
sectional radius of rods or thickness of sheets
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Guinier Analysis size of any kind of object
0 1
0.0 Guinier analysis for compact particlesI0=1 ± 6.4344e-06Rg=77.627 ± 0.0078715 Å
-0.2
-0.1Q
))
Sphere Data Guinier fit Guinier fit
Qmax*Rg=0.4301
-0.4
-0.3
Ln(P
(Q
-0.5
0.4
Guinier analysis for compact particlesI0=1.002 ± 0.00022913Rg=78.747 ± 0.037728 ÅQmax*Rg=1.2359
-0.6250x10-6200150100500
Q2 (Å-2)
Qmax g
Å49 Managed by UT-Battelle
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Precise Rg is 77.46 Å
Guinier Analysis size of any kind of object
0 1
0.0 Guinier analysis for compact particlesI0=1.0048 ± 3.6871e-05Rg=76.96 ± 0.034883 ÅQmax*Rg=0.49062
-0.2
-0.1Q
))
Rod Data Guinier fit Guinier fit
Qmax Rg 0.49062
0 4
-0.3
Ln(P
(Q
-0.5
-0.4
Guinier analysis for compact particlesI0=0.99866 ± 0.00072094Rg=73.297 ± 0.1302 ÅQ *R =1 1402
Å
-0.6250x10-6200150100500
Q2 (Å-2)
Qmax Rg 1.1402
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Precise Rg is 77.46 Å Q ( )
Modified Guinier Analysis for object extended in 1 dimension
-4.6 Rod Data Modified Guinier fit for rods
-5.0
-4.8
(arb
.))
-5.4
-5.2
Ln(Q
*I(Q
)
-5.8
-5.6L
Modified Guinier analysis for rodlike formsIC=0.012324 ± 3.027e-05Rc=9.0941 ± 0.01747 ÅQmax*Rc=1.3143
√ Å Å
-6.040x10-33020100
Q2 (Å-2)
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Rod radius = √2 * Rc = 12.9 Å, exact radius = 13.3 Å
Guinier Analysis size of any kind of object
0.0
-0.2
-0.1
Q))
Disk Data Guinier fit
0 4
-0.3
Ln(P
(Q
-0.5
-0.4Guinier analysis for compact particlesI0=1.0047 ± 3.8683e-05Rg=77.136 ± 0.0064846 ÅQmax*Rg=1.2106
Å
-0.6250x10-6200150100500
Q2 (Å-2)
max g
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Precise Rg is 77.46 Å Q ( )
Pair correlation function and shape
D
P(r) : inverse Fourier transform of scattering function : Probability of fi di t f l th b t Dmax
rfinding a vector of length r between scattering centers within the scattering particle.
4
3
2(r)
4
3
2
4
3
2
4
3
2
4
3
2 2
1
00 20 40 60 80
P( 21
00 10 20 30 40 50
2
1
00 10 20 30 40 50
2
1
00 20 40 60 80
2
1
00 10 20 30 40 50
Shape : Modeled as a uniform density distribution that best fits the scattering data.
r (Å) Dmax
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fits the scattering data.
SAS Form Factor Modeling of great use in biologyg gy
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SAS Form Factor Modeling of great use in biologyg gy
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Two-component Systems / Compound Objectsj
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Two-Component Systems
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Two-Component SystemsRg as function of contrast
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Interparticle Structure Factor S(Q)
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S(Q) and Pair Correlation Function
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S(Q) and Statistical Thermodynamics
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Surface Scattering - Porod
B t f t l h i t f Q x 3 462 Managed by UT-Battelle
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But, fractal rough interfaces: Q-x , 3 < x < 4
Structural Hierarchy (particulate)
Structural information viewed on five length scales. Structural features at larger length scales areobserved at smaller Q.
Adapted from DW Schaefer MRS Symposium Proceeding 1987
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Scattering analysis that describes hierarchical structures: Mass Fractal (Teixeira), UnifiedFit (Beaucage) combine power law scattering ranges with Rg transitions
Non-particulate Scattering
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SAS Summary• SAS applications are in the nm to μm range and
otherwise only limited by imagination.• SAS is used alone but often complementary to other • SAS is used alone, but often complementary to other
methods, e.g. microscopy.• Scattering is similar to diffraction (but different).• SAS data analysis can be tough math, or make use of
readily available approximations, models and software.software.
• SAS does not see atoms but larger interesting features over many length scales.
Å• Precision of structural parameters can be 1Å or better.
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