DOCSLIB.ORG

Glossary, Descriptions and Definitions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Glossary, Descriptions and Definitions Electro Optical Components, Inc. 5460 Skylane Boulevard, Santa Rosa, CA 95403 Toll Free: 855-EOC-6300 www.eoc-inc.com | [email protected] 5.1. Infrared (IR) Photodetectors Glossary noise, improve high frequency performance and increase the 5.1. Infrared (IR) Photodetectors dynamic range. Unfortunately, at the expense of flicker noise (1/f) in most cases. Infrared photodetectors are semiconductor electro-optical devices that convert infrared radiation into an electrical signal. Photovoltaic detectors are more vulnerable to electrostatic dis- charges than photoconductors. Hg1-xCdxTe Photoelectromagnetic detectors (PEM) Known also as Mercury Cadmium Telluride (MCT), HgCd- Photovoltaic detectors are based on the photoelectromagnetic Te, (Cd,Hg)Te or MerCadTel. It is a variable ba nd gap alloy, effect based on spatial separation of optically generated elec- commonly used for fabrication of photodetectors with tunable trons and holes in the magnetic field. The devices do not re- spectral response. quire electrical bias and show no flicker noise (1/f). The PEM 5 devices are typically used as fast, uncooled detectors of the long wavelength radiation. InAs1-xSbx InAs Sb also known as Indium Arsenide Antimonide and In- 1-x x Detector formats AsSb is another variable band gap alloy used for fabrication of Detector formats photodetectors with tunable spectral response. Square or rectangular formats are typically used for any IR detectors. Circular geometry is soSquaremetim ore rectangulars used fo formatsr pho tareod itypicallyodes. used for any IR de- Physical detector area A Detector formats tectors. Circular geometry is sometimes used for photodiodes. Square or rectangEuqlaur ivfoarmleantst samre atyllp siciagllny auls dede tfeocr taonry cIRir cduetiet ctors. Circular geometry is Active area of a detector where the incidentsom radiationetimes uiss eabd- fEorlEquivalent epchtortiocd ipordoeps small.e rties signal of so detectorme phot ocircuitdetec tors can be described by the small signal detector sorbed and sensed. ‧ Equivalent smallc sirigcunaitl dwehteicchto rc coirncsuisitt s of photocurrent source Iph =Ri P, detector dynamic resistance Rsh , Electric properties of some photodetectors can be described Electric propertiesc abyopf aasc osmallimtaen cpsignaleh oCto detector,d eatencdto rscircuitse rciaens which bre sdi seconsiststsacnribce d of R bphotocursy . tRhes iss-m tahlle s ipganaral sdietitce crteors istance of the devices that Optical detector area Ao ‧ circuit which conrseisdtus coef aphvoatiolacburlere npt hsootuorccuer rIephn =tR. i UPn, fdoerteucntaort edlyy,n athmeic sriemsipsltea nmceo dReshl , cannot accurately describe rent source Iph=RiP, detector dynamic resistance Rsh, capaci- capacitance C , andtance ser iC,es andres seriesistanc resistancee R . R Ris. Rth eis pa aparasiticrasitic rresistanceesistanc eof of the devices that The apparent optical area of the detector which is “seen”. It is properties of long wasvelsens gtsh photodiodes operating at near room temperatures. reduce available phtheoto devicescurren tthat. U nreducefortun availableately, th photocurrent.e simple mo Unfortunately,del cannot a ccurately describe equal to physical area of the detector active element unless an optical concentrator is used. The optical detectorproper tareaies ocanf lo beng wtheave simplelength model phot ocannotdiode accuratelys operati ndescribeg at ne apropertiesr room te ofm longper atures. significantly magnified in detectors supplied with optical con- wavelength photodiodes operating at near room temperatures. centrators, for i.e., immersion lenses (see Optical immersion chapter). Photoconductors (PC) Photoconductive detectors based on the photoconductive effect. Infrared radiation generates charge carriers in the semiconductor active region decreasing its resistance. The resistance change is sensed as a current change by applying a constant voltage bias. The devices are characterized by near linear current-voltage characteristics. The electric field in pho- Figure 1. Equivalent small signal circuit of toconductors is constant across the device. It equals ratio of an IR photodetector bias voltage and distance between contacts Figure 1. EquivaleFnti gsmuraell 1si.g nEaql ucivrcauliet notf small signal circuit of an IR photodetector E= V/L an IR photodetector Photocurrent The optimum bias voltage is specified in the final test report and depends on detector size, operating temperature and spectral Photocurrent is a current generated by IR radiation, which is response. Photocurrent not in thermal equilibrium with detector. For small irradiation, Photocurrent is thPe hthecou rtphotocurrentroecntu grerennerta tise proportionald by IR rad itoat iincidenton, wh iradiationch is no tpower in the Prmal equilibrium with detector. For smaPll ihrroatdoiactuiornre, nthte i sp htohteoc cuurrrernetn ist pgreonpeortaiotneadl tboy i nIcRid reandt iraatdiioantio, nw phoicwhe ri sP not in thermal equilibrium with Photovoltaic detectors (PV, PVM) I = R ·P detector. For small irraphd iatiio n, the photocurrent is proportional to incident radiation power P where R is the current responsivity. Photovoltaic detectors (photodiodes) are semiconductori I = R ·P where R is the current responsivity. ph i structures with one (PV) or multiple (PVM),C homo-urren tor re heterospon-siwvihtye rRei Ri is the current responsivity. junctions. Absorbed photons produce charge carriers that are i Current responsivity (A/W) is the ratio of photocurrent and power of radiation. The current collected at the contacts, resulting in external photocurrent. CuCurrentrrent r eresponsivitysponsivity R Photodiodes have complex current voltageres pcharacteristics.onsivity is t ypically measured for moni ochromatic radiation (the spectral current responsivity) and blackbody radiation (the blackbody current responsivity). The responsivity The devices can operate either at flicker-free zero bias or with CuCurrentrrent responsivityresponsi v(A/W)ity ( Ais /aW ratio) i sof tphotocurrenthe ratio o andf p hpowoto- current and power of radiation. The current typically remains constant for weak radiation and tends to decrease with more strong reverse voltage. Reverse bias voltage is frequently applied to reersp ofo nradiation.sivity Theis tcurrentypica lresponsivityly meas uisr etypicallyd for measuredmonoc hromatic radiation (the spectral current increase responsivity, differential resistance,ra dreduceiation . the shot reforsp monochromaticonsivity) and radiation blackb (theod yspectral radia currenttion ( tresponsivihe blac-kbody current responsivity). The responsivity Current responsitvyiptyic-laelnlyg thre pmroadinusc t cRoi·Lns tant for weak radiation and tends to decrease with more strong The current responsivity of unbiased PEM, PVM and biased (with constant electric field E) 52 radiation. www.vigo.com.pl PC detectors is proportional to the reciprocal length. Therefore, the current responsivity Ri ·L is used to comparCe uderrveicnets roef svaproionus ifvoirtmya-ltse.n gth product Ri·L Another normalizTehd e ccuurrrernetn tr ersepsopnosnivsitiyv, ityR i ·oLf/ Eu, nbisi ausseedd PtEo Mc,o mPpVaMre arnedsp obniassiveitdy (owf ith constant electric field E) photoconductive devices of various format, and operating with different electric fields. PC detectors is proportional to the reciprocal length. Therefore, the current responsivity Ri ·L Maximum bias voislt augse dV tmoa xc ompare devices of various formats. The maximum voltage that can be applied to a photoconductor or p hotovoltaic detector Another normalized current responsivity, Ri ·L/E, is used to compare responsivity of without a risk of itsp hdaomtoacgoen. ductive devices of various format, and operating with different electric fields. Dark current I dark V The current that flMowasx iinm au pmho tboidaeste vctoolrt iang thee rmmaal xe quilibrium with its surrounding. The maximum voltage that can be applied to a photoconductor or photovoltaic detector without a risk of its damage. Dark current Idark The current that flows in a photodetector in thermal equilibrium with its surrounding. Detector formats DSeqtueacrteo ro fro rrmecattasn gular formats are typically used for any IR detectors. Circular geometry is S sqDouematreec ttiomorr e rfesoc rutmasneagdtus fl aorr fpohrmotaotds ioadree sty. pically used for any IR detectors. Circular geometry is sSoqmueatriem eosr urescetda nfogru plahro tfoodrmioadtess .a re typically used for any IR detectors. Circular geometry is Equivalent small signal detector circuit sometimes used for photodiodes. EEquleivcatrliecn pt rsompaelrlt iseisg noafl dseotmecet oprh coirtocudiet tectors can be described by the small signal detector Electric properties of some photodetectors can be described by the small signal detector Ecqiruciuviat lewnht iscmh acllo snisginsatsl doeft epchtorto cciurcrrueint t source I =R ‧P , detector dynamic resistance R , ‧ph i sh circuit which consists of photocurrent source Iph =Ri P, detector dynamic resistance Rsh , Electric proper tie s of some photodetector s ca n be described by the small signal detector capacitance C, and series resistan c e R s . Rs is the parasitic resistance of the devices that capacitance C, and series resistance Rs . Rs is the parasitic resistance of the devices that circuit which consists of photocurrent source I =R ‧P , detector dynamic resistance R , rerdeudcuec ea vaavilabilaleb pleh opthocoutorrceunrtr. eUnnt.f oUrtnufnoartteulny,a theely ,ps hitmhepil es imopdlee l mcaondneol t caacncnuorat tealcy cduersacterilbye dshescribe
Load more

Recommended publications
  • Quantum Coherence and Control in One-And Two-Photon Optical Systems
    Quantum coherence and control in one- and two-photon optical systems Andrew J. Berglund∗ Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA and Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, NM 87545, USA We investigate coherence in one- and two-photon optical systems, both theoretically and ex- perimentally. In the first case, we develop the density operator representing a single photon state subjected to a non-dissipative coupling between observed (polarization) and unobserved (frequency) degrees of freedom. We show that an implementation of “bang-bang” quantum control protects pho- ton polarization information from certain types of decoherence. In the second case, we investigate the existence of a “decoherence-free” subspace of the Hilbert space of two-photon polarization states under the action of a similar coupling. The density operator representation is developed analytically and solutions are obtained numerically. [Note: This manuscript is taken from the author’s un- photon polarization-entangled state that, due to its sym- dergraduate thesis (A.B. Dartmouth College, June 2000, metry properties, is immune to collective decoherence advised by Dr. Walter E. Lawrence), an experimental of the type mentioned above. That is, this state is a and theoretical investigation under the supervision of Dr. decoherence-free subspace (DFS) of the Hilbert space of Paul G. Kwiat.1] photon polarization [6, 7]. Photon pairs entangled in both polarization and frequency degrees of freedom, such as hyper-entangled photons produced in down-conversion I. INTRODUCTION sources (see [8, 9]), further complicate this particular de- coherence mechanism . In particular, energy conserva- tion imposes frequency correlations which affect the co- Decoherence in two-state quantum systems is a sig- herence properties of these two-photon states.
    [Show full text]
  • Lecture Notes
    Solid State Physics PHYS 40352 by Mike Godfrey Spring 2012 Last changed on May 22, 2017 ii Contents Preface v 1 Crystal structure 1 1.1 Lattice and basis . .1 1.1.1 Unit cells . .2 1.1.2 Crystal symmetry . .3 1.1.3 Two-dimensional lattices . .4 1.1.4 Three-dimensional lattices . .7 1.1.5 Some cubic crystal structures ................................ 10 1.2 X-ray crystallography . 11 1.2.1 Diffraction by a crystal . 11 1.2.2 The reciprocal lattice . 12 1.2.3 Reciprocal lattice vectors and lattice planes . 13 1.2.4 The Bragg construction . 14 1.2.5 Structure factor . 15 1.2.6 Further geometry of diffraction . 17 2 Electrons in crystals 19 2.1 Summary of free-electron theory, etc. 19 2.2 Electrons in a periodic potential . 19 2.2.1 Bloch’s theorem . 19 2.2.2 Brillouin zones . 21 2.2.3 Schrodinger’s¨ equation in k-space . 22 2.2.4 Weak periodic potential: Nearly-free electrons . 23 2.2.5 Metals and insulators . 25 2.2.6 Band overlap in a nearly-free-electron divalent metal . 26 2.2.7 Tight-binding method . 29 2.3 Semiclassical dynamics of Bloch electrons . 32 2.3.1 Electron velocities . 33 2.3.2 Motion in an applied field . 33 2.3.3 Effective mass of an electron . 34 2.4 Free-electron bands and crystal structure . 35 2.4.1 Construction of the reciprocal lattice for FCC . 35 2.4.2 Group IV elements: Jones theory . 36 2.4.3 Binding energy of metals .
    [Show full text]
  • Exploring Quantum Vacuum with Low-Energy Photons 3
    August 29, 2018 8:19 WSPC/INSTRUCTION FILE paper International Journal of Quantum Information c World Scientific Publishing Company EXPLORING QUANTUM VACUUM WITH LOW-ENERGY PHOTONS E. MILOTTI,∗ F. DELLA VALLE INFN - Sez. di Trieste and Dip. di Fisica, Universit`adi Trieste via A. Valerio 2, I-34127 Trieste, Italy G. ZAVATTINI, G. MESSINEO INFN - Sez. di Ferrara and Dip. di Fisica, Universit`adi Ferrara via Saragat 1, Blocco C, I-44122 Ferrara, Italy U. GASTALDI, R. PENGO, G. RUOSO INFN - Lab. Naz. di Legnaro viale dell’Universit`a2, I-35020 Legnaro, Italy D. BABUSCI, C. CURCEANU, M. ILIESCU, C. MILARDI INFN, Laboratori Nazionali di Frascati, CP 13, Via E. Fermi 40, I-00044, Frascati (Roma), Italy Although quantum mechanics (QM) and quantum field theory (QFT) are highly suc- cessful, the seemingly simplest state – vacuum – remains mysterious. While the LHC experiments are expected to clarify basic questions on the structure of QFT vacuum, much can still be done at lower energies as well. For instance, experiments like PVLAS try to reach extremely high sensitivities, in their attempt to observe the effects of the interaction of visible or near-visible photons with intense magnetic fields – a process which becomes possible in quantum electrodynamics (QED) thanks to the vacuum fluc- tuations of the electronic field, and which is akin to photon-photon scattering. PVLAS is now close to data-taking and if it reaches the required sensitivity, it could provide arXiv:1210.6751v1 [physics.ins-det] 25 Oct 2012 important information on QED vacuum. PVLAS and other similar experiments face great challenges as they try to measure an extremely minute effect.
    [Show full text]
  • 1940 the Connection Between Spin and Statistics1
    W. Pauli, Phys. Rev., Vol. 58, 716 1940 The Connection Between Spin and Statistics1 W. Pauli Princeton, New Jersey (Received August 19, 1940) —— ♦ —— Reprinted in “Quantum Electrodynamics”, edited by Julian Schwinger —— ♦ —— Abstract In the following paper we conclude for the relativistically invari- ant wave equation for free particles: From postulate (I), according to which the energy must be positive, the necessity of Fermi-Dirac statistics for particles with arbitrary half-integral spin; from postulate (II), according to which observables on different space-time points with a space-like distance are commutable, the necessity of Einstein-Base statistics for particles with arbitrary integral spin. It has been found useful to divide the quantities which are irreducible against Lorentz transformations into four symmetry classes which have a commutable multiplication like +1, −1, +, − with 2 = 1. 1This paper is part of a report which was prepared by the author for the Solvay Congress 1939 and in which slight improvements have since been made. In view of the unfavorable times, the Congress did not Cake place, and the publication of the reports has been postponed for an indefinite length of time. The relation between the present discussion of the connection between spin and statistics, and the somewhat less general one of Belinfante, based on the concert of charge invariance, has been cleared up by W. Pauli and J. Belinfante, Physica 7, 177 (1940). 1 § 1. UNITS AND NOTATIONS Since the requirements of the relativity theory and the quantum theory are fundamental for every theory, it is natural to use as units the vacuum velocity of light c, and Planck’s constant divided by 2π which we shall simply denote by ~.
    [Show full text]
  • Simultaneous Measurement of Rotational and Translational Diffusion of Anisotropic Colloids with a New Integrated Setup for Fluorescence Recovery After Photobleaching
    Home Search Collections Journals About Contact us My IOPscience Simultaneous measurement of rotational and translational diffusion of anisotropic colloids with a new integrated setup for fluorescence recovery after photobleaching This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2012 J. Phys.: Condens. Matter 24 245101 (http://iopscience.iop.org/0953-8984/24/24/245101) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 131.211.152.249 The article was downloaded on 22/05/2012 at 11:06 Please note that terms and conditions apply. IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 24 (2012) 245101 (15pp) doi:10.1088/0953-8984/24/24/245101 Simultaneous measurement of rotational and translational diffusion of anisotropic colloids with a new integrated setup for fluorescence recovery after photobleaching B W M Kuipers, M C A van de Ven, R J Baars and A P Philipse Van’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands E-mail: [email protected] Received 20 February 2012, in final form 10 April 2012 Published 8 May 2012 Online at stacks.iop.org/JPhysCM/24/245101 Abstract This paper describes an integrated setup for fluorescence recovery after photobleaching (FRAP) for determining translational and rotational Brownian diffusion simultaneously, ensuring that these two quantities are measured under exactly the same conditions and at the same time in dynamic experiments. The setup is based on translational-FRAP with a fringe pattern of light for both the bleaching and monitoring of fluorescently labeled particles, and rotational-FRAP, which uses the polarization of a short bleach light pulse to create a polarization anisotropy.
    [Show full text]
  • Physics Notes
    PHYSICSENGLISH NOTESNOTES © The Institute of Education 20120157 SUBJECT: LeavingPhysics Cert English LEVEL: Higher and Ordinary Level TEACHER: Denis Creaven TEACHER: Pat Doyle Topics Covered:Covered: Yeats’sSound & Poetry Waves - Themes and Styles About Pat:Denis: DenisPat graduated has been with an a English Masters teacher Degree inat PhysicsThe Institute in 1986 of and Education has taught for Physics over 30 in theyears Institute and hasfor over instilled 30 years. a love He hasof the been English a regular language contributor in generations to Science Plus, of astudents. Science and Mathematics publication for the Leaving Cert. He recently co-wrote Exploring Science, Exploring Science Workbook and Revise Wise Science for the Junior Certificate. Sound and Waves The Doppler Effect You are standing on the side of a road listening to the sound from a siren on the roof of a stationary car that is 500 m down the road. The car starts to move towards you and you notice that the frequency of the sound is different (higher). The car passes by you and moves away from you. The frequency of the sound is different again (lower). This is due to the Doppler effect. Definition of Doppler effect: The Doppler effect is the apparent change in the frequency of a wave due to the relative motion between source and observer. Explanation of Doppler effect: Source moving towards Stationary observer Source moving away observer from observer (i) wavefronts closer together (i) wavefronts further apart (ii) observed wavelength smaller (ii) observer wavelength longer (iii) observed frequency higher (iii) observed frequency lower The observed wavelength and frequency change as the source moves past observer !!!!!!!!!! Demonstration (laboratory) experiment for the Doppler Effect: A battery powered electronic buzzer is attached to a string 50 cm long.
    [Show full text]
  • Thoroughly Testing Einstein's Special Relativity
    Journal of Modern Physics, 2016, 7, 87-105 Published Online January 2016 in SciRes. http://www.scirp.org/journal/jmp http://dx.doi.org/10.4236/jmp.2016.71009 Thoroughly Testing Einstein’s Special Relativity Theory, and More Mario Rabinowitz Armor Research, Redwood City, CA, USA Received 3 December 2015; accepted 18 January 2016; published 22 January 2016 Copyright © 2016 by author and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract Einstein’s Special Relativity (ESR) has enjoyed spectacular success as a mathematical construct and in terms of the experiments to which it has been subjected. Possible vulnerabilities of ESR will be explored that break the symmetry of reciprocal observations of length, time, and mass. It is 22 shown how Newton could also have derived length contraction L′ = L0 1 − vc. Einstein’s Gen- eral Relativity (EGR) will also be discussed occasionally such as a changed perspective on gravita- tional waves due to a small change in ESR. Some additional questions addressed are: Did Einstein totally eliminate the Ether? Is the physical interpretation of ESR completely correct? Why should there be a maximum speed limit, and should it always be the same? The mass-energy equation is 22 revisited to show that in 1717 Newton could have derived the modern m≈− m0 1 vc, and not known that it violates the foundation of his mechanics. Tributes are paid to Einstein and others. Keywords Vulnerabilities of Special Relativity, Challenge of Reciprocal Observations of Length and Time, Einstein, Newton, Galilean Transformation, Thought Experiments, General Relativity, Gravitational Waves 1.
    [Show full text]
  • Wave Mechanics in the Light of the Reciprocal System Prof
    The Wave Mechanics In the Light of the Reciprocal System Prof. K.V.K. Nehru, Ph. D. One of the large areas to which the Reciprocal System is yet to be applied in detail is spectroscopy. The need is all the more urgent as vast wealth of empirical data is available here in great detail and a general theory must explain all the aspects. To be sure, this was one of the earlier areas which Larson 1 explored. But he soon found out, he writes, that there were complications too many and too involved that he decided to postpone the investigation until more basic ground was developed by studying other areas. Coupled with this is also the fact that the calculation of the properties of elements like the lanthanides is still beyond the scope of the Reciprocal System as developed to date.2 The question of the appropriateness of the Periodic Table as given by Larson is still open.2,3,4,5 Under these circumstances it is certain that there is lot more to be done toward enlarging the application of the Reciprocal System to the intrinsic structure of the atom. Perhaps it is time to break new ground in the exploration of the mechanics of the time region, the region inside unit space. Breaking new ground involves some fresh thinking and leaving no stone unturned. In this context, it may be desirable to examine, once again, such a successful theory as the Wave Mechanics in the light of our existing knowledge of the Reciprocal System. 1 The Fallacies of the Wave Mechanics The fundamental starting point of the Wave Mechanics is the correlation, which Louis de Broglie advanced originally, of a wave with a moving particle.
    [Show full text]
  • Formulate Equations for Reciprocity Vector and Scalar of Some Mechanical and Electrical Quantities by Faisal A
    Global Journal of Science Frontier Research: A Physics and Space Science Volume 15 Issue 1 Version 1.0 Year 2015 Type : Double Blind Peer Reviewed International Research Journal Publisher: Global Journals Inc. (USA) Online ISSN: 2249-4626 & Print ISSN: 0975-5896 Formulate Equations for Reciprocity Vector and Scalar of Some Mechanical and Electrical Quantities By Faisal A. Mustafa Babylon University, Iraq Abstract- This study deals a new concepts of some physical reciprocally quantities which are vectors or scalars and its relationship with the fundamental quantities. The reciprocal of kinematics dimension quantities of moved particle for linear, rotational and circular movement are resulted the quantities that so called the time quantities such as time velocity, time acceleration. Other derivative quantities were derived from the principle equations to produce reciprocal movement equations. For dynamical mechanics, the quantities were derived from the principle equation such as time force, momentum, torque, energy,…ect. Also some reciprocal quantities due to electricity equations include the reactance, electric current, conductivity, …ect, and its derivative quantities are introduced time current density, time power. Keywords: reciprocal of velocity, conductivity, reciprocal current , inverse quantity, reciprocal , time electric field. GJSFR-A Classification : FOR Code: 240402 FormulateEquations forReciprocityVectorandScalarofSomeMechanicalandElectricalQuantities Strictly as per the compliance and regulations of : © 2015. Faisal A. Mustafa. This is a research/review paper, distributed under the terms of the Creative Commons Attribution- Noncommercial 3.0 Unported License http://creativecommons.org/licenses/by-nc/3.0/), permitting all non commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Formulate Equations for Reciprocity Vector and Scalar of Some Mechanical and Electrical Quantities Faisal A.
    [Show full text]
  • Introduction to Crystallography and Electron Diffraction Marc De Graef Carnegie Mellon University
    Introduction to Crystallography and Electron Diffraction Marc De Graef Carnegie Mellon University Sunday July 24, 2016 M&M Conference, July 24-28, 2016, Columbus, OH Overview Introductory remarks Basic crystallographic concepts Diffraction basics Dynamical electron scattering Basics of cross-correlations 3 A dual view of the world measuring stick measuring stick S S -> distance between trees: d = 1 [S] -> # trees per unit S: r = 2 [S-1] S’ S’ -> distance between trees: d = 1/2 [S’] -> # trees per unit S’: r = 4 [S’-1] numerical value of d decreases when numerical value of r increases when length of measuring stick increases length of measuring stick increases -> d is contravariant quantity -> r is covariant quantity real or direct space reciprocal space 4 A dual view of the world distance between lattice planes: lattice plane “lineal density”: d [nm] g [nm-1] we use distances to describe the [nm-1] is also the unit of a spatial coordinates of atoms, usually gradient (d/dx), and a gradient scaled in appropriate units evokes the concept of “normal”… -> we need a tool to compute distances, -> we need a tool to compute normals angles, etc… and lineal densities real or direct space reciprocal space 5 Real or Direct Space 3-D lattices are represented by a parallelepiped or unit cell; the edge lengths and angles between the edges make up the lattice parameters; the contravariant view There are seven different unit cell types, known as the crystal systems: Parallelepiped : “a 6-faced polyhedron all of whose faces are parallelograms lying in pairs of parallel planes” 6 14 Bravais lattices 7 Lattice geometry Each lattice node can be reached by means of a translation from the origin.
    [Show full text]
  • Chapter 4.Pdf
    4. Matter waves 27 electrons 70 electrons 735 electrons 1 by 1920 shortcomings of Bohr’s model - can not explain intensity of spectral lines - limited success for multi electron systems but crucial to Bohr’s model are integer numbers (n), and integers otherwise in physics only in wave phenomena such as interference back to light: E = h f, so photons are energy, E = mc2, so photons are “kind of matter” although mass less, light is a wave, c = ? f E h f h Einstein 1906: p = /c = /c must also be = / ? (we used this to explain Compton effect) de Broglie 1923 PhD thesis speculation; because photons have wave and particle characteristics, perhaps all forms of matter, e.g. electron, have wave as well as particle h E h properties, p = / ? for all particles, f = / h , ? = /p If that turns out to be true, I’ll quit physics, Max von Laue, Noble Laureate 1914, author of “Materiewelleninterferenzen” the classical text on electron diffraction (what if p = m v = 0 because particle is not moving, v = 0, h is a constant, so ? must be infinite – can’t be), consequence particles can never be truly at rest, v and p can be very very very low, but never zero!!!!! 2 that is what is actually observed: a tiny tiny pendulum will be hit by air molecules and move all the time somewhat irregularly, a large pendulum will obey classical physics in other words: electrons and everything else also has a dual particle-wave character, an electron is accompanied by a wave (not an electromagnetic wave!!!) which guides/pilots the electron through space first great idea that
    [Show full text]
  • An Ahistorical Approach to Elementary Physics
    An Ahistorical Approach to Elementary Physics B.C. Regan1,2, ∗ 1Department of Physics and Astronomy, University of California, Los Angeles, California 90095, U.S.A. 2California NanoSystems Institute, University of California, Los Angeles, California 90095, U.S.A. (Dated: October 21, 2020) A goal of physics is to understand the greatest possible breadth of natural phenomena in terms of the most economical set of basic concepts. However, as the understanding of physics has developed historically, its pedagogy and language have not kept pace. This gap handicaps the student and the practitioner, making it harder to learn and apply ideas that are ‘well understood’, and doubtless making it more difficult to see past those ideas to new discoveries. Energy, momentum, and action are archaic concepts repre- senting an unnecessary level of abstraction. Viewed from a modern perspective, these quantities correspond to wave parameters, namely temporal frequency, spatial frequency, and phase, respectively. The main results of classical mechanics can be concisely repro- duced by considering waves in the spacetime defined by special relativity. This approach unifies kinematics and dynamics, and introduces inertial mass not via a definition, but rather as the real-space effect of a reciprocal-space invariant. I. INTRODUCTION it is possible, and indeed easier, to access and admire the full power of the approximate theories if they are not Physics is customarily taught following the same cloaked in classical language, which was developed well chronological order in which it was developed. Students before the underlying and unifying ideas were discovered. first learn the classical mechanics of Galileo and Newton, The goal here is to present a formulation of classical then the classical electricity and magnetism of Faraday mechanics that is concise and more closely based on our and Maxwell, and then more modern topics such as spe- current, best understanding of physics as a whole.
    [Show full text]