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Phasing of Three Dimensional Diffraction Patterns from Finite-Sized ObjectsPowerPoint Presentation

Phasing of Three Dimensional Diffraction Patterns from Finite-Sized Objects

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Phasing of Three Dimensional Diffraction Patterns from Finite-Sized Objects

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Phasing of Three Dimensional Diffraction Patterns from Finite-Sized Objects

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- Ian Robinson
- Ivan Vartanyants
- Mark Pfeifer
- John Pitney
- Garth Williams
- Sébastien Boutet

Department of Physics

University of Illinois

SSRL Imaging Workshop,

October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

- Coherence in Diffraction
- The Phase Problem
- Nanocrystal Shapes
- Crystallization of Proteins
- Applications at LCLS

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

- Thermodynamic fluctuations
- No ensemble average in CXD

- Probe of structure on nm scale
- 1D, 2D and 3D
- non-periodic object gives continuous F(q)

- Oversampling (in reciprocal space) permits solution of the phase problem

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

Coherent region defined by slits

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

J. R. Fienup Appl. Opt. 21 2758 (1982)

R. W. Gerchberg and W. O. Saxton Optik 35 237 (1972)

I. K. Robinson, SSRL Imaging Workshop, October 2002

- ‘Positivity’ constraint
- Finite support, molecular envelope
- Solvent flattening
- Molecular replacement
- Non-crystallographic symmetry
- Basis of ‘direct methods’ (Sayre, Bricogne)
- Non-uniqueness is ‘pathologically rare’ (d>1)

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

Annalen der Physik [5] 26 55 (1936)

“Stacheln”

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

- Au blanket film
- Quartz substrate
- Annealed at 950°C for 70 hrs.

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

kf

Q=kf - ki

ki

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

I. K. Robinson, SSRL Imaging Workshop, October 2002

- 50 frames
- 30sec exposure
- 0.3sec playback
- 150x200 pixels of 22.5μm

I. K. Robinson, SSRL Imaging Workshop, October 2002

- “Diffuse” scattering acquires fine structure
- Phase problem solved by oversampling
- Images of small particles in 3D
- Applications of CXD at LCLS
- (physics) fluctuations at the atomic level
- (biology) imaging of viruses and proteins

I. K. Robinson, SSRL Imaging Workshop, October 2002