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Summer School 2012 Marite Cardenas HCØ D312 Neutron reflectivity’s day Today you will learn about specular scattering and non- specular scattering. Scattering length and contrast matching in Soft Matter. Theory of Reflection. Optics apply to Light, Neutrons and X-rays are all waves. Reflect over the different information that can be extracted from each of these waves Learn to read a reflectivity curve. Some cases in neutron reflection. Tommy Nylander LU Hanna Wacklin ESS Marité Cárdenas KU
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Summer School 2012 Marite Cardenas HCØ D312 What is reflectivity? Reflectivity refers to the fraction of incident radiation (amplitude) that is reflected by a surface. reflected by a surface Why is reflectivity interesting for us? Reflectivity reveals interfacial structure 1.Layer thickness 2.Layer composition 3.In plane structure air-water air-solid solid-liquid
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Summer School 2012 Marite Cardenas HCØ D312 Light, X-rays and Neutrons can be treated as waves: Same principles apply to any of them! What are the advantages of X-rays and neutrons over light? x-rays and neutrons have much shorter wavelength than light -> they can explore much smaller spacing (of the order of molecular dimensions).
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 Or take advantage of radiation wavelength q z = 4 * sinθ Neutrons do have different energies, right?
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Summer School 2012 Marite Cardenas HCØ D312
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 And this is how it goes when you work in our field
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Summer School 2012 Marite Cardenas HCØ D312 If things were just so easy… have you forget about the phase problem in scattering?
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Summer School 2012 Marite Cardenas HCØ D312 The refractive index The real part can be expressed as: n = 1 – 2 /2ρ For X-ray, For Neutron, ρ= Σ n i f i e 2 / mc 2 ρ= Σ n i b i n i is the number density for the nuclear specie i b i is the scattering length of nuclear specie i f i is the atomic factor for specie I
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Summer School 2012 Marite Cardenas HCØ D312 The refractive index The real part can be expressed as: n = 1 – 2 /2ρ Since ρ is very small, n ~ 1 GRAZING INCIDENCE is a MUST for neutrons and X-rays θ qzqz
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Summer School 2012 Marite Cardenas HCØ D312 WHY such dependency for protein/DNA as compared to lipid? H/D exchange! What’s the deal with bio-molecules? NRW Deuterated lipid/protein/DNA 65432106543210 Lipid head group
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching air = 0 D2O = 6.35 water can be adjusted by the ratio of H 2 O/D 2 O. The lipid chain can also be fully or partially deuterated.
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching air = 0 water = 0
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching air = 0 water = headgroup
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching air = 0 water = lipid 2
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching air = 0 water = air By controlling the degree of D substitution in the lipid, the lipid can be contrast matched to the protein
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Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching Taken from http://rktchem..ox.ac.uk/research.html
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Summer School 2012 Marite Cardenas HCØ D312 SO NOW YOU SHOULD BE READY FOR THE REAL STUFF!
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