Prozorov_33 - PHYSICS 222 Introduction to Classical Physics...

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Unformatted text preview: PHYSICS 222 Introduction to Classical Physics II Prof. Ruslan Prozorov Iowa State University Fall 2011 LECTURES 33 X-ray diffraction. Holography. X - rays Hand mit Ringen (Hand with Rings): print of Wilhelm Röntgen's first "medical" Xray, of his wife's hand, taken on 22 December 1895 and presented to Ludwig Zehnder of the Physik Institut, University of Freiburg, on 1 January 1896 Wilhelm Conrad Röntgen 27 March 1845 - 10 February 1923 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 2 x - rays PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 3 producing x-rays PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 4 x-ray diffraction PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 5 x-ray diffraction X-rays have a wavelength commensurate with atomic structure. Rontgen had only discovered X-rays a few decades earlier when Friederich, Knipping, and von Laue used it to elucidate crystal structures between adjacent ions in salt crystals. PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 6 von Laue apparatus PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 7 what happens? PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 8 constructive PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University destructive 11 November 2011 9 atomic configurations from x-ray scattering PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 10 revealing crystal structure PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 11 the analysis: Bragg’s law 2d sin m m 1, 2,3... PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 12 table salt PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 13 spacing between atomic planes PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 14 typical workflow PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 15 x-ray scattering led to understanding DNA An x-ray scattering pattern recorded by Dr. Franklin led Watson and Crick to discover the doublehelix structure of DNA PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 16 DNA structure from x-ray PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 17 difficulties and solutions • One of the main difficulties in X-ray crystallography is determining phases in the diffraction pattern. • Because no X-ray lens exists, X-rays cannot be used to form an image of the crystal being diffracted, and hence phase information is lost. • Fortunately, electron microscopes contain electron lenses, and so the crystallographic structure factor phase information can be experimentally determined in electron crystallography. • Aaron Klug was the first to realize that the phase information could be read out directly from the Fourier transform of an electron microscopy image that had been scanned into a computer, already in 1968. • For this, and his studies on virus structures and transfer-RNA, Klug received the Nobel Prize for chemistry in 1982. PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 18 electrons are waves and can diffract direct electron – microscope image and CALCULATED diffractogram PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University measured diffractogram can determine structure with greater precision than direct imaging 11 November 2011 19 quasicrystals Nobel Prize 2011 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University Ho-Mg-Zn quasicrystal 11 November 2011 20 holography PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 21 reconstruction PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 22 holography By using a beam splitter, coherent laser radiation can illuminate an object from different perspective. Interference effects provide the depth that makes a three-dimensional image from two-dimensional views. PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 23 holography—theoretical PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 24 holography - examples PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 25 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 26 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 27 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 28 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 29 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 30 sin 1 1.22 PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University D 11 November 2011 31 exam example A camera lens with focal length of f = 50 mm and maximum aperture f/2 forms an image of an object 9.0 m away. if the resolution is diffraction limited, what is the distance between two points on the object that can be resolved on the image? 50 mm The aperture diameter is: D / f number 25 mm 2 then, the angular diffraction – limited separation is: 500 109 m sin 1.22 1.22 2.4 105 D 25 103 m S L sin 9.0 2.4 105 0.22 mm PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 32 multiple views of the same event PHYS222 - Lecture 33 - Prof. Ruslan Prozorov - Iowa State University 11 November 2011 33 ...
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This note was uploaded on 11/14/2011 for the course PHYS 5863005 taught by Professor Meyer during the Fall '09 term at Iowa State.

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