100 Years of X-ray Diffraction Helmut Dosch SXNS-12 DESY Kolkatta, July 25, 2012 Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 1 The Discovery of X-ray Diffraction A rather disputed scientific revolution Text book: Laue experiment intended to use a 3d-grating to select from the continuous x-ray spectrum the monochromatic Laue interference spots 100 years later: we know better ……*) *) says Michael Eckert, Deutsches Museum, Munich Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 2 1895-1912 Nature of x-rays and the discovery of x-ray diffraction Munich around 1900 . 1894 Boltzmann leaves Munich (to Vienna) strong supporter of atomistic theory (opposed to Planck) . 1900 Röntgen accepts appointment to Munich creates a big institutes . 1904 Boltzmann chair renewed . 1909 Sommerfeld to Munich new theory institute (academic novelty) Sommerfeld creates the famous theory school Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page2012│Page 3 1895-1912 Nature of x-rays and the discovery of x-ray diffraction The Sommerfeld School Cafe Lutz, Hofgarten well-known meeting place Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 4 1895-1912 Nature of x-rays and the discovery of x-ray diffraction The Sommerfeld School Sommerfeld Students Hans Bethe Werner Heisenberg Wolfgang Pauli Linus Pauling Peter Debye Isaac Rabi Max von Laue ….. ….. Debye Laue Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 5 1895 -1912 Nature of x-rays and the discovery of x-ray diffraction . 1906 Arnold Sommerfeld (before his call to Munich in a letter to Wilhelm Wien) “Isn’t it a shame that ten years after Röntgen’s discovery one still does not know what is going on with X-rays” . 1899 Hermann Haga and Cornelis H. Wind (Dutch physicists) passage of X-rays through narrowing slits Haga and Wind interpreted a diffuse broadening at the narrower end of the slit as a diffraction phenomenon. Sommerfeld regarded X-rays as a shower of electromagnetic square pulses and estimated from the experiments of Haga and Wind that the order of magnitude of the width of an X-ray pulse is of the order of 1 A . 1908 Charles Glover Barkla new evidence about the nature of X-rays: appear in two varieties. a/ independent of the material, polarizable, Bremsstrahlung (related to Sommerfeld´s elmag pulses) b/ like fluorescence radiation, nonpolarizable, materials dependent . 1910/11 William Henry Bragg (father) „Neutral pair hypothesis“: X-rays as particles. based on the speculation that an electron on encountering an atom may neutralize its charge and takes the form of the X-ray (travelling with almost speed of light) He got in a serious conflict with his son Lawrence Bragg who promoted the wave picture and discovered Bragg´s Law (see below) William Henry B. Lawrence B. (1909-1913 Rutherford experiments at Manchester, 1911 publication on existence of a nucleus) Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 6 1895 -1912 Nature of x-rays and the discovery of x-ray diffraction . Since discovery of x-rays: various attempts to see interference effects 1897 W.C. Röntgen no effect observed, since then, crystals had often been the target of beams of X-ray without the slightest indication of any interference effect . 1911 1st Solvay Conference “Theorie der Strahlung und Quanten” (Leiden, H.A. Lorentz) A. Sommerfeld: “h Hypothesis” in microscopic processes: action (not energy) is quantized ! Stopping of cathode-ray electron: E t = h Planck Sommerfeld Lorentz Rutherford Einstein Solvay M. Curie Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 7 1895 -1912 Nature of x-rays and the discovery of x-ray diffraction . Sommerfeld wanted to put the h-hypothesis under experimental scrutiny in his own institute in Munich . for this task (!) he hired Walter Friedrich, in 1911 as an “experimental assistant” student of W.C Röntgen, short rivalry between Sommerfeld and Röntgen “Röntgen wants Friedrich for himself” Friedrich´s experiments were dragging on without any conclusive results . 1909 Max von Laue joins Sommerfeld as Privatdozent PhD Student of Max Planck “Theory of interferences at parallel plates” . Other assistant of Sommerfeld: Peter Debye came with Sommerfeld from Aachen Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 8 1895-1912 Approaching the X-ray Diffraction Experiment . 1910 Paul-Peter Ewald joins Sommerfeld to carry out his dissertation Sommerfeld always had a long list of open problems ranging from hydrodynamics to wave propagation in wireless telegraphy all involving complex partial differential equations (elliptical integrals) end of the list: Optical properties of an anisotropic arrangements of isotropic responators (Sommerfeld excused for this last one, as he admitted that he himself had no idea how to tackle it) Heavy math involved: concept of Fourier transform not available . Ewald finished his thesis Dec 1911 Disturbing result: no propagation possible, apart from singular paths Ewald desired to discuss this with Laue: English Garden 1912 Laue questions: “Why did you place the resonators on a regular lattice ?” (seemingly unaware of the crystal hypothesis) “What is the distance between the resonators ?” (Ewald: not know, but around nanometers) Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 9 1895-1912 Nature of x-rays and the discovery of x-ray diffraction . 1912 Laue proposes the înterference experiment to Sommerfeld Laue: “Interference from Barkla´s fluorescence-like x-rays” (fundamental misconcept of Laue !) Sommerfeld declined “Fluorescence is incoherent, cannot give interference” ! Laue secretly lured Walter Friedrich and Paul Knipping away from the “h-hypothesis project” to this interference experiment (this caused a major long-lasting personal problem between Sommerfeld and Laue) Paul Knipping PhD student of Röntgen later joined SIEMENS . April 20, 1912: First Interference Phenomena first data on Cu2SO4 ⋅ 5 H2O good crystals Barkla ! „fluorescence misconception“ Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 10 1895-1912 Nature of x-rays and the discovery of x-ray diffraction Presentation of Laue´s experiment at the Bavarian Academy of Science June 8, 1912 Bavarian Academy of Science Participants: „Aaahhh“ Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 11 1895-1912 Nature of x-rays and the discovery of x-ray diffraction Many physicists were puzzled by the Munich discovery and von Laue´s explanation as an interference of the crystal’s own fluorescence radiation. Henry Moseley letter to his mother in fall 1912: Died very young st “The men who did the work entirely failed to understand what it meant, during 1 world war in Gallipoli and give an explanation which was obviously wrong”, . William and Lawrence Bragg 1912: they didnot believe Laue´s explanation either, but started also wrong (biased by Bragg father´s particle view): X-ray particles travelling through regular alleys in a crystal (today: „channeling“) . Nov 11, 1912: Lawrence Bragg reported at Cambridge on the Munich Experiment followed by his interpretation as an interference of x-ray waves from parallel lattice planes within the crystal 2d 풔풊풏 휽 = l Lawrence Bragg dismissed Laue´s interpretation and his fathers channeling interpretation Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 12 1895-1912 Nature of x-rays and the discovery of x-ray diffraction 1913/14 W.L. Bragg und W.H. Bragg solve the first crystal structures NaCl, Diamond, Calcite, … using their concept of x-ray reflection from lattice planes. Note: Crystal structure determination rather tedious until early 1960 (all calculations by hand) • First transistor-based computers: 1956: CADET (Transistor Electronic Digital Automatic Computer) Can´t Add Doesn´t Even Try 1959-1970: IBM 1620 punch card computer Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 13 Paul-Peter Ewald The architect of the modern theory of x-ray diffraction Article in Physikalische Zeitschrift (June 1913) Ewald, P.P. Phys. Z. 14, 465-472 (1913) Ewald construction, reciprocal space concept Reconciliation between Bragg´s reflection and Laue´s diffraction concepts. 1933 Ewald emigrated to United States Ewald died Aug 25, 1985 in Ithaca (Hans A. Bethe (Cornell) married a daugther of Ewald) Nobel Awards 1914 Max von Laue (Physics) 1915 W.H. and W.L. Bragg (Physics) 1917 Charles Barkla (Physics) 1932 Werner Heisenberg (Physics) 1936 Peter Debye (Chemistry) (no Nobel awards for Sommerfeld and Ewald) Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page2012│Page 14 von Laue 1959 in Lindau April 24, 1960 died in a car accident Cemetary Göttingen Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 15 Observation Understanding Control Continua Diskrete Systeme Quantum Control Mechanics Fluctuations of Electrodynamics Atoms, Molecules Matter and Thermodynamics Quantummechanics Energy Max von Laue you are here derived from G. Fleming Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 16 The new (X-ray) Challenge Ordered Structures Locally Ordered Structures Equilibrium Phenomena Nonequilibrium Phenomena Phase Diagrams Transient States coherent x-ray sources Era of Crystalline Matter Era of Complex Matter 1912 2012 future Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page2012│Page 17 My special thanks to Dr. Michael Eckert Deutsches Museum, Munich (for the materials and interesting discussions) Helmut Dosch│100 Years of X-Ray Diffraction │SXNS-12, Kolkata 2012│Page 18 .