1. 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

2. 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

3. 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).

4. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

5. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

6. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

7. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

8. Summer School 2012 Marite Cardenas HCØ D312 Or take advantage of radiation wavelength q z = 4  * sinθ Neutrons do have different energies, right?

9. Summer School 2012 Marite Cardenas HCØ D312

10. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

11. Summer School 2012 Marite Cardenas HCØ D312 Taken from http://rktchem..ox.ac.uk/research.html

12. Summer School 2012 Marite Cardenas HCØ D312 And this is how it goes when you work in our field

13. Summer School 2012 Marite Cardenas HCØ D312 If things were just so easy… have you forget about the phase problem in scattering?

14. Summer School 2012 Marite Cardenas HCØ D312 The refractive index The real part can be expressed as: n = 1 – 2 /2ρ 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

15. Summer School 2012 Marite Cardenas HCØ D312 The refractive index The real part can be expressed as: n = 1 – 2 /2ρ Since ρ is very small, n ~ 1 GRAZING INCIDENCE is a MUST for neutrons and X-rays θ qzqz

16. 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

17. 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.

18. Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching  air = 0  water = 0

19. Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching  air = 0  water =  headgroup

20. Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching  air = 0  water =  lipid 2

21. 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

22. Summer School 2012 Marite Cardenas HCØ D312 The art of contrast matching Taken from http://rktchem..ox.ac.uk/research.html

23. Summer School 2012 Marite Cardenas HCØ D312 SO NOW YOU SHOULD BE READY FOR THE REAL STUFF!