6. Basic Properties of Atoms
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Franck-Hertz Experiment
IIA2 Modul Atomic/Nuclear Physics Franck-Hertz Experiment This experiment by JAMES FRANCK and GUSTAV LUDWIG HERTZ from 1914 (Nobel Prize 1926) is one of the most impressive comparisons in the search for quantum theory: it shows a very simple arrangement in the existence of discrete stationary energy states of the electrons in the atoms. ÜÔ ÖÑÒØ Á Á¾ ¹ ÜÔ ÖÑÒØ This experiment by JAMES FRANCK and GUSTAV LUDWIG HERTZ from 1914 (Nobel Prize 1926) is one of the most impressive comparisons in the search for quantum theory: it shows a very simple arrangement in the existence of discrete stationary energy states of the electrons in the atoms. c AP, Department of Physics, University of Basel, September 2016 1.1 Preliminary Questions • Explain the FRANCK-HERTZ experiment in our own words. • What is the meaning of the unit eV and how is it defined? • Which experiment can verify the 1. excitation energy as well? • Why is an anode used in the tube? Why is the current not measured directly at the grid? 1.2 Theory 1.2.1 Light emission and absorption in the atom There has always been the question of the microscopic nature of matter, which is a key object of physical research. An important experimental approach in the "world of atoms "is the study of light absorption and emission of light from matter, that the accidental investigation of the spectral distribution of light absorbed or emitted by a particular substance. The strange phenomenon was observed (first from FRAUNHOFER with the spectrum of sunlight), and was unexplained until the beginning of this century when it finally appeared: • If light is a continuous spectrum (for example, incandescent light) through a gas of a particular type of atom, and subsequently , the spectrum is observed, it is found that the light is very special, atom dependent wavelengths have been absorbed by the gas and therefore, the spectrum is absent. -
The Franck-Hertz Experiment: 100 Years Ago and Now
The Franck-Hertz experiment: 100 years ago and now A tribute to two great German scientists Zoltán Donkó1, Péter Magyar2, Ihor Korolov1 1 Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, Hungary 2 Physics Faculty, Roland Eötvös University, Budapest, Hungary Franck-Hertz experiment anno (~1914) The Nobel Prize in Physics 1925 was awarded jointly to James Franck and Gustav Ludwig Hertz "for their discovery of the laws governing the impact of an electron upon an atom" Anode current Primary experimental result 4.9 V nobelprize.org Elv: ! # " Accelerating voltage ! " Verh. Dtsch. Phys. Ges. 16: 457–467 (1914). Franck-Hertz experiment anno (~1914) The Nobel Prize in Physics 1925 was awarded jointly to James Franck and Gustav Ludwig Hertz "for their discovery of the laws governing the impact of an electron upon an atom" nobelprize.org Verh. Dtsch. Phys. Ges. 16: 457–467 (1914). Franck-Hertz experiment anno (~1914) “The electrons in Hg vapor experience only elastic collisions up to a critical velocity” “We show a method using which the critical velocity (i.e. the accelerating voltage) can be determined to an accuracy of 0.1 V; its value is 4.9 V.” “We show that the energy of the ray with 4.9 V corresponds to the energy quantum of the resonance transition of Hg (λ = 253.6 nm)” ((( “Part of the energy goes into excitation and part goes into ionization” ))) Important experimental evidence for the quantized nature of the atomic energy levels. The Franck-Hertz experiment: 100 years ago and now Franck-Hertz experiment: published in 1914, Nobel prize in 1925 Why is it interesting today as well? “Simple” explanation (“The electrons ....”) → description based on kinetic theory (Robson, Sigeneger, ...) Modern experiments Various gases (Hg, He, Ne, Ar) Modern experiment + kinetic description (develop an experiment that can be modeled accurately ...) → P. -
Bohr Model of Hydrogen
Chapter 3 Bohr model of hydrogen Figure 3.1: Democritus The atomic theory of matter has a long history, in some ways all the way back to the ancient Greeks (Democritus - ca. 400 BCE - suggested that all things are composed of indivisible \atoms"). From what we can observe, atoms have certain properties and behaviors, which can be summarized as follows: Atoms are small, with diameters on the order of 0:1 nm. Atoms are stable, they do not spontaneously break apart into smaller pieces or collapse. Atoms contain negatively charged electrons, but are electrically neutral. Atoms emit and absorb electromagnetic radiation. Any successful model of atoms must be capable of describing these observed properties. 1 (a) Isaac Newton (b) Joseph von Fraunhofer (c) Gustav Robert Kirch- hoff 3.1 Atomic spectra Even though the spectral nature of light is present in a rainbow, it was not until 1666 that Isaac Newton showed that white light from the sun is com- posed of a continuum of colors (frequencies). Newton introduced the term \spectrum" to describe this phenomenon. His method to measure the spec- trum of light consisted of a small aperture to define a point source of light, a lens to collimate this into a beam of light, a glass spectrum to disperse the colors and a screen on which to observe the resulting spectrum. This is indeed quite close to a modern spectrometer! Newton's analysis was the beginning of the science of spectroscopy (the study of the frequency distri- bution of light from different sources). The first observation of the discrete nature of emission and absorption from atomic systems was made by Joseph Fraunhofer in 1814. -
Sterns Lebensdaten Und Chronologie Seines Wirkens
Sterns Lebensdaten und Chronologie seines Wirkens Diese Chronologie von Otto Sterns Wirken basiert auf folgenden Quellen: 1. Otto Sterns selbst verfassten Lebensläufen, 2. Sterns Briefen und Sterns Publikationen, 3. Sterns Reisepässen 4. Sterns Züricher Interview 1961 5. Dokumenten der Hochschularchive (17.2.1888 bis 17.8.1969) 1888 Geb. 17.2.1888 als Otto Stern in Sohrau/Oberschlesien In allen Lebensläufen und Dokumenten findet man immer nur den VornamenOt- to. Im polizeilichen Führungszeugnis ausgestellt am 12.7.1912 vom königlichen Polizeipräsidium Abt. IV in Breslau wird bei Stern ebenfalls nur der Vorname Otto erwähnt. Nur im Emeritierungsdokument des Carnegie Institutes of Tech- nology wird ein zweiter Vorname Otto M. Stern erwähnt. Vater: Mühlenbesitzer Oskar Stern (*1850–1919) und Mutter Eugenie Stern geb. Rosenthal (*1863–1907) Nach Angabe von Diana Templeton-Killan, der Enkeltochter von Berta Kamm und somit Großnichte von Otto Stern (E-Mail vom 3.12.2015 an Horst Schmidt- Böcking) war Ottos Großvater Abraham Stern. Abraham hatte 5 Kinder mit seiner ersten Frau Nanni Freund. Nanni starb kurz nach der Geburt des fünften Kindes. Bald danach heiratete Abraham Berta Ben- der, mit der er 6 weitere Kinder hatte. Ottos Vater Oskar war das dritte Kind von Berta. Abraham und Nannis erstes Kind war Heinrich Stern (1833–1908). Heinrich hatte 4 Kinder. Das erste Kind war Richard Stern (1865–1911), der Toni Asch © Springer-Verlag GmbH Deutschland 2018 325 H. Schmidt-Böcking, A. Templeton, W. Trageser (Hrsg.), Otto Sterns gesammelte Briefe – Band 1, https://doi.org/10.1007/978-3-662-55735-8 326 Sterns Lebensdaten und Chronologie seines Wirkens heiratete. -
Knowledge on the Web: Towards Robust and Scalable Harvesting of Entity-Relationship Facts
Knowledge on the Web: Towards Robust and Scalable Harvesting of Entity-Relationship Facts Gerhard Weikum Max Planck Institute for Informatics http://www.mpi-inf.mpg.de/~weikum/ Acknowledgements 2/38 Vision: Turn Web into Knowledge Base comprehensive DB knowledge fact of human knowledge assets extraction • everything that (Semantic (Statistical Web) Web) Wikipedia knows • machine-readable communities • capturing entities, (Social Web) classes, relationships Source: DB & IR methods for knowledge discovery. Communications of the ACM 52(4), 2009 3/38 Knowledge as Enabling Technology • entity recognition & disambiguation • understanding natural language & speech • knowledge services & reasoning for semantic apps • semantic search: precise answers to advanced queries (by scientists, students, journalists, analysts, etc.) German chancellor when Angela Merkel was born? Japanese computer science institutes? Politicians who are also scientists? Enzymes that inhibit HIV? Influenza drugs for pregnant women? ... 4/38 Knowledge Search on the Web (1) Query: sushi ingredients? Results: Nori seaweed Ginger Tuna Sashimi ... Unagi http://www.google.com/squared/5/38 Knowledge Search on the Web (1) Query:Query: JapaneseJapanese computerscomputeroOputer science science ? institutes ? http://www.google.com/squared/6/38 Knowledge Search on the Web (2) Query: politicians who are also scientists ? ?x isa politician . ?x isa scientist Results: Benjamin Franklin Zbigniew Brzezinski Alan Greenspan Angela Merkel … http://www.mpi-inf.mpg.de/yago-naga/7/38 Knowledge Search on the Web (2) Query: politicians who are married to scientists ? ?x isa politician . ?x isMarriedTo ?y . ?y isa scientist Results (3): [ Adrienne Clarkson, Stephen Clarkson ], [ Raúl Castro, Vilma Espín ], [ Jeannemarie Devolites Davis, Thomas M. Davis ] http://www.mpi-inf.mpg.de/yago-naga/8/38 Knowledge Search on the Web (3) http://www-tsujii.is.s.u-tokyo.ac.jp/medie/ 9/38 Take-Home Message If music was invented Information is not Knowledge. -
Rutherford's Atomic Model
CHAPTER 4 Structure of the Atom 4.1 The Atomic Models of Thomson and Rutherford 4.2 Rutherford Scattering 4.3 The Classic Atomic Model 4.4 The Bohr Model of the Hydrogen Atom 4.5 Successes and Failures of the Bohr Model 4.6 Characteristic X-Ray Spectra and Atomic Number 4.7 Atomic Excitation by Electrons 4.1 The Atomic Models of Thomson and Rutherford Pieces of evidence that scientists had in 1900 to indicate that the atom was not a fundamental unit: 1) There seemed to be too many kinds of atoms, each belonging to a distinct chemical element. 2) Atoms and electromagnetic phenomena were intimately related. 3) The problem of valence (원자가). Certain elements combine with some elements but not with others, a characteristic that hinted at an internal atomic structure. 4) The discoveries of radioactivity, of x rays, and of the electron Thomson’s Atomic Model Thomson’s “plum-pudding” model of the atom had the positive charges spread uniformly throughout a sphere the size of the atom with, the newly discovered “negative” electrons embedded in the uniform background. In Thomson’s view, when the atom was heated, the electrons could vibrate about their equilibrium positions, thus producing electromagnetic radiation. Experiments of Geiger and Marsden Under the supervision of Rutherford, Geiger and Marsden conceived a new technique for investigating the structure of matter by scattering particles (He nuclei, q = +2e) from atoms. Plum-pudding model would predict only small deflections. (Ex. 4-1) Geiger showed that many particles were scattered from thin gold-leaf targets at backward angles greater than 90°. -
Application of Ion Scattering Techniques to Characterize Polymer Surfaces and Interfaces
Materials Science and Engineering R 38 (2002) 107±180 Application of ion scattering techniques to characterize polymer surfaces and interfaces Russell J. Compostoa,*, Russel M. Waltersb, Jan Genzerc aLaboratory for Research on the Structure of Matter, Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA bDepartment of Chemical Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA cDepartment of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA Abstract Ion beam analysis techniques, particularly elastic recoil detection (ERD) also known as forward recoil spectrometry (Frcs) has proven to be a value tool to investigate polymer surfaces and interfaces. A review of ERD, related techniques and their impact on the field of polymer science is presented. The physics of the technique is described as well as the underlying principles of the interaction of ions with matter. Methods for optimization of ERD for polymer systems are also introduced, specifically techniques to improve the depth resolution and sensitivity. Details of the experimental setup and requirements are also laid out. After a discussion of ERD, strategies for the subsequent data analysis are described. The review ends with the breakthroughs in polymer science that ERD enabled in polymer diffusion, surfaces, interfaces, critical phenomena, and polymer modification. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Ion scattering; Polymer surface; Polymer interface; Elastic recoil detection; Forward recoil spectrometry; Depth profiling 1. Introduction Breakthroughs in polymer science typically correlate with the discovery and application of new experimental tools. One of the first examples was the prediction by P.J. Flory that the single chain conformation in a dense system (i.e. -
1 CHEM 1411 Chapter 5 Homework Answers 1. Which Statement Regarding the Gold Foil Experiment Is False?
1 CHEM 1411 Chapter 5 Homework Answers 1. Which statement regarding the gold foil experiment is false? (a) It was performed by Rutherford and his research group early in the 20th century. (b) Most of the alpha particles passed through the foil undeflected. (c) The alpha particles were repelled by electrons (d) It suggested the nuclear model of the atom. (e) It suggested that atoms are mostly empty space. 2. Ernest Rutherford's model of the atom did not specifically include the ___. (a) neutron (b) nucleus (c) proton (d) electron (e) electron or the proton 3. The gold foil experiment suggested ___. (a) that electrons have negative charges (b) that protons have charges equal in magnitude but opposite in sign to those of electrons (c) that atoms have a tiny, positively charged, massive center (d) the ratio of the mass of an electron to the charge of an electron (e) the existence of canal rays 4. Which statement is false? (a) Ordinary chemical reactions do not involve changes in nuclei. (b) Atomic nuclei are very dense. (c) Nuclei are positively charged. (d) Electrons contribute only a little to the mass of an atom (e) The nucleus occupies nearly all the volume of an atom. 2 5. In interpreting the results of his "oil drop" experiment in 1909, ___ was able to determine ___. (a) Robert Millikan; the charge on a proton (b) James Chadwick; that neutrons are also present in the nucleus (c) James Chadwick; that the masses of protons and electrons are nearly identical (d) Robert Millikan; the charge on an electron (e) Ernest Rutherford; the extremely dense nature of the nuclei of atoms 6. -
Rutherford Scattering
Chapter 5 Lecture 4 Rutherford Scattering Akhlaq Hussain 1 5.5 Rutherford Scattering Formula Rutherford’s experiment of 훼-particles scattering by the atoms in a thin foil of gold revealed the existence of positively charged nucleus in the atom. ➢ The 훼-particles were scattered in all directions. ➢ Some passes undeflected by the foil. ➢ Some were scattered through larger angles even back scattered. ➢ The only valid explanation of large angle deflection was if the total positive charge were concentrated at some small region. ➢ Rutherford called it nucleus. 2 5.5 Rutherford Scattering Formula ′ 풖ퟏ 3 5.5 Rutherford Scattering Formula Consider an incident charge particle with charge z1e is scattered through a target with charge z2e. The trajectory of scattered particles is a hyperbola as shown. The trajectory of the particles in repulsive field with origin at o' is shown. In the case of attractive force, center will be at “o”. when particles are apart at large distance, the total energy it posses is in form of Kinetic energy ′ 1 ′ 2 푘 = ൗ2 µ푢1 = 퐸 ′ 2퐸 푢1 = µ 4 5.5 Rutherford Scattering Formula 푆 푑푠 We have to find 휎 휃′ = 푠푖푛 휃′ 푑휃′ ′ 푙 = µ푢1푆 = 푆 2µ퐸 Where S is the impact parameter. The trajectory is hyperbola, from equation of conic 훼 = 푒 cos 훼 − 1 and for 푟 → ∞ 푟 1 1 ⇒ cos 훼 = = 푒 2퐸푙2 1+ µ푘2 From the figure 2훼 + 휃′ = 휋 휋−휃′ 훼 = 2 휋−휃′ 휃′ Now cot 훼 = cot = tan 5 2 2 5.5 Rutherford Scattering Formula 휃′ cot 훼 = tan 2 휃′ cos 훼 cos 훼 tan = = 2 sin 훼 1−푐표푠2훼 휃′ cos 훼 tan = 2 1 cos 훼 −1 푐표푠2훼 휃′ 1 tan = 2 1 −1 푐표푠2훼 휃′ 1 1 tan = = 2 푒2−1 2퐸푙2 1+ −1 휇푘2 6 5.5 Rutherford Scattering Formula −1Τ 휃′ 2퐸푙2 2 tan = 2 휇푘2 휃′ 푘 휇 푘 tan = = ′ 2퐸 2 푙 2퐸 푙푢′ Because 푢 = 1 1 µ ′ Since 푙 = µ푢1S 휃′ 푘 ⇒ tan = ′2 2 푆µ푢1 Differentiating with θ' above equation can be written as. -
Communications-Mathematics and Applied Mathematics/Download/8110
A Mathematician's Journey to the Edge of the Universe "The only true wisdom is in knowing you know nothing." ― Socrates Manjunath.R #16/1, 8th Main Road, Shivanagar, Rajajinagar, Bangalore560010, Karnataka, India *Corresponding Author Email: [email protected] *Website: http://www.myw3schools.com/ A Mathematician's Journey to the Edge of the Universe What’s the Ultimate Question? Since the dawn of the history of science from Copernicus (who took the details of Ptolemy, and found a way to look at the same construction from a slightly different perspective and discover that the Earth is not the center of the universe) and Galileo to the present, we (a hoard of talking monkeys who's consciousness is from a collection of connected neurons − hammering away on typewriters and by pure chance eventually ranging the values for the (fundamental) numbers that would allow the development of any form of intelligent life) have gazed at the stars and attempted to chart the heavens and still discovering the fundamental laws of nature often get asked: What is Dark Matter? ... What is Dark Energy? ... What Came Before the Big Bang? ... What's Inside a Black Hole? ... Will the universe continue expanding? Will it just stop or even begin to contract? Are We Alone? Beginning at Stonehenge and ending with the current crisis in String Theory, the story of this eternal question to uncover the mysteries of the universe describes a narrative that includes some of the greatest discoveries of all time and leading personalities, including Aristotle, Johannes Kepler, and Isaac Newton, and the rise to the modern era of Einstein, Eddington, and Hawking. -
Rutherford Scattering
Rutherford Scattering MIT Department of Physics (Dated: September 24, 2014) This is an experiment which studies scattering alpha particles on atomic nuclei. You will shoot alpha particles, emitted by 241Am, at thin metal foils and measure the scattering cross section of the target atoms as a function of the scattering angle, the alpha particle energy, and the nuclear charge. You will then measure the intensity of alpha particles scattered by thin metal foils as a function of the scattering angle for several elements of very different atomic number. PREPARATORY QUESTIONS within which the electrons occupy certain positions of equilibrium, like raisins in a pudding. Set in motion, Please visit the Rutherford Scattering chapter on the the electrons should vibrate harmonically, radiating elec- 8.13x website at mitx.mit.edu to review the background tromagnetic energy with characteristic sharp frequencies material for this experiment. Answer all questions found that would be in the optical range if the radii of the −8 in the chapter. Work out the solutions in your laboratory atomic spheres were of the order of 10 cm. However, notebook; submit your answers on the web site. the \raisin pudding" model yielded no explanation of the numerical regularities of optical spectra, e.g. the Balmer formula for the hydrogen spectrum and the Ritz combi- SUGGESTED PROGRESS CHECK FOR END OF nation principle [3] for spectra in general. 2nd SESSION At this point, Ernest Rutherford got the idea that the structure of atoms could be probed by observing Plot the rate of alpha particle observations for 10◦ and the scattering of alpha particles. -
Lecture 11 Ion Beam Analysis
1 AP 5301/8301 Instrumental Methods of Analysis and Laboratory Lecture 11 Ion Beam Analysis Prof YU Kin Man E-mail: [email protected] Tel: 3442-7813 Office: P6422 2 Lecture 8: outline . Introduction o Ion Beam Analysis: an overview . Rutherford backscattering spectrometry (RBS) o Introduction-history o Basic concepts of RBS – Kinematic factor (K) – Scattering cross-section – Depth scale o Quantitative thin film analysis o RBS data analysis . Other IBA techniques o Hydrogen Forward Scattering o Particle induced x-ray emission (PIXE) . Ion channeling o Minimum yield and critical angle o Dechanneling by defects o Impurity location 3 Analytical Techniques 100at% 10at% AES XRD IBA 1at% 0.1at% RBS XRF 100ppm TOF- 10ppm SIMS 1ppm TXRF 100ppb Detection Range Detection 10ppb Chemical bonding DynamicS 1ppb Elemental information IMS Imaging information 100ppt Thickness and density information 10ppt Analytical Spot size But IBA is typically quantitative and depth sensitive http://www.eaglabs.com 4 Ion Beam Analysis: an overview Inelastic Elastic Incident Ions Rutherford backscattering (RBS), resonant scattering, Nuclear Reaction Analysis channeling (NRA) p, a, n, g Particle induced x-ray emission (PIXE) Defects generation Elastic recoil detection Ion Beam Absorber foil Modification 5 Ion Beam Analysis 1977 2009 2014 1978 6 Why IBA? . Simple in principle . Fast and direct . Quantitative (without standard for RBS) . Depth profiling without chemical or physical sectioning . Non-destructive . Wide range of elemental coverage . No special specimen