DOCSLIB.ORG

Comparative Study of Radiation-Induced Optical Behavior of Quartz Glasses and Sapphire Crystals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Comparative Study of Radiation-Induced Optical Behavior of Quartz Glasses and Sapphire Crystals The Sixth International Conference "Modern Problems of Nuclear Physics", September 19-22,2006 R MPNP'2006 One can conclude from our findings that the most probable model for 243nm absorption band and for 400 nm luminescence is the center of oxygen vacancy with two neighboring atoms of silicon and germanium (=Si-Ge=). We also find that not an essential change in intensity of 243nm absorption band is observed as the irradiation dose increases. Moreover, 400nm luminescence band shows decrease in intensity. The observed radiation-induced effects seem to related to y-radiation, which causes a change in local surroundings of initial defect state (=Si-Ge=) and lengthen thus bonds between Ge and Si (=Si —Ge=). In this case, depending on local surroundings there can be both vacancies, which are incapable to produce luminescence, and vacancies, which have ordinary bonds between atoms (=Si-Ge=) and become luminescence centers. In this picture, the absorption band in the vicinity of 243nm must present for both of the types of defects. UZ0603140 COMPARATIVE STUDY OF RADIATION-INDUCED OPTICAL BEHAVIOR OF QUARTZ GLASSES AND SAPPHIRE CRYSTALS Nuritdinov I., Islamov A.K., Amonov M.Z., Boboyerova S.G. Institute of Nuclear Physics, Tashkent, Uzbekistan Different parameters of plasma in accelerators and fusion reactors, such as density, temperature, dynamics of relaxation, are often estimated by emission in the optical spectral range. So that optics of detecting devices (windows, lenses, etc.) should be transparent in the range of 170-1200nm. Their parameters, however, appear to be changed under radiation influence (fast neutrons, gamma-quanta etc). It may lead to misrepresenting of useful signal due to both transparency decreasing and undesirable radiation stimulated luminescence of optical material. In this connection comparative study of the radiation damage of optical absorption and luminescent behaviors of KU-1 quartz glass and sapphire crystals was undertaken with the aim to predict to what extent the properties of these materials may degrade in the field of radiation. The samples were bombarded with neutrons of the fluencies lO'MO20 cm"2 (neutron flux 1013 cm s"1, E>0.1MeV) and gamma-irradiated in the dose interval of 106-1010 Rad (60Co, E=1.25MeV, gamma dose rate 670R/s). It should be noted, however, that such a huge fluencies and dose couldn't be reached in real conditions. In the gamma dose interval mentioned sapphire crystals do not show any additional absorption bands. On the contrary KU-1 quartz glass exhibits the radiation-induced absorption band peaked at 215nm, the intensity of which is increased with gamma dose up to 5.108R with following saturation. At the same time the transparency in the spectral range of 300-900nm doesn't decrease significantly. Sapphire crystals show gamma-stimulated luminescence in the range 300-330nm while quartz glasses do not emit under gamma excitation at room temperature. Neutron bombardment leads to deep coloration of sapphire crystals but does not change the transparency of quartz glasses in the spectral range of 300-600nm. At the same time neutron irradiation causes the appearance of gamma-luminescence in both materials. Quartz glasses show two luminescence bands at 470 and 650nm, intensity of which is increased with neutron fluence and saturated at the fluence 1019cm~2. Two gamma-luminescence bands at 330nm (F^-centre) and 228 Section II. Radiation Physics of Condensed Matter The Sixth International Conference "Modem Problems of Nuclear Physics", September 19-22, 2006 420nm (F-centre) appear in sapphire crystals after neutron irradiation. Their intensity is increased with neutron fluence up to 1018 cm"2 and then decreased. It should be noted that gamma- luminescence intensity in sapphire crystals is ten times larger in magnitude than in quartz glasses is. From the date obtained one can conclude that both materials may be applied to design optical elements for nuclear sets with neutron flux less than 1012cm"V\ In these conditions the rate of accumulation of intrinsic radiation defects would be less and, consequently, the extent of degradation of transparency and luminescence appearance would depend on initial disordering of material. UZ0603141 QUANTUM CRITICAL POINTS AND THEIR ROLE IN fflGH-Tc SUPERCONDUCTIVITY, STRIPE AND PSEUDOGAP FORMATION IN HOLE-DOPED CUPRATES Dzhumanov S. Institute of Nuclear Physics, Tashkent, Uzbekistan The discovery of the new copper oxide (cuprate) high-7^ superconductors (HTSC) and the intensive studies of the physical properties of these materials have led to the revolutionary era in condensed matter physics [1]. After this discovery, it has become clear that these high-7c cuprates deviate most strongly from conventional low-rc superconductors, both in the normal and in the superconducting (SC) state [1,2]. The breakdown of the well-known one-electron band theory, Fermi-liquid and BCS pairing theories (see Refs. [1, 2]) occurs in a wide range of the phase diagrams of the hole-doped cuprates, and the competitions between different ground states of the cuprates in a substantial region of the phase diagrams, lead to the occurrence of the distinct pseudogaps (PGs) and quantum critical points (QCPs) and to the stripe formation in these systems. The high-7^ superconductivity in the hole-doped cuprates occurs also in this region of their phase diagrams. Although much experimental and theoretical works have been carried out in the past two decades, they have not yet reached any conclusive understanding on the electronic phase diagrams of these high-Tc cuprates, and on the distinct QCPs and their role in high-j^ superconductivity, stripe and PG formation. The exotic properties of the high-rc cuprates and their understanding require radically new theoretical approaches and physical concepts. In this work, we discuss the possible origins of the QCPs, metal-insulator transitions, PGs, dynamic (metallic or SC) and static (insulating) stripes, and high-re superconductivity in hole-doped cuprates. We develop the new and more pertinent theoretical approaches and methods for studying the quantum criticality and the existence of the distinctly different QCPs in these materials at the strong electron-phonon interactions and to examine the role played by the QCPs in high~rc superconductivity, PG behavior and stripe formation in the cuprate HTSC. We obtain quantitatively the real and adequate phase diagrams of the hole-doped cuprates and focus on key questions related to the entire phase diagram of the different cuprates, from underdoped to heavily overdoped region. This should allow us to check whether the usual Fermi-liquid and BCS pairing theories valid also for the cases of the intermediate and strong electron-phonon coupling regimes or they break down. We show that the QCPs, dynamic and static stripes, PG behavior and unconventional high-rc superconductivity are emerged in hole-doped cuprates in the strong . 229 Section II. Radiation Physics of Condensed Matter.
Load more

Recommended publications
  • Dozy-Chaos Mechanics for a Broad Audience
    challenges Concept Paper Dozy-Chaos Mechanics for a Broad Audience Vladimir V. Egorov Russian Academy of Sciences, FSRC “Crystallography and Photonics”, Photochemistry Center, 7a Novatorov Street, 119421 Moscow, Russia; [email protected] Received: 29 June 2020; Accepted: 28 July 2020; Published: 31 July 2020 Abstract: A new and universal theoretical approach to the dynamics of the transient state in elementary physico-chemical processes, called dozy-chaos mechanics (Egorov, V.V. Heliyon Physics 2019, 5, e02579), is introduced to a wide general readership. Keywords: theoretical physics; quantum mechanics; molecular quantum transitions; singularity; dozy chaos; dozy-chaos mechanics; electron transfer; condensed matter; applications 1. Introduction In a publication of Petrenko and Stein [1], it is demonstrated that “the feasibility of the theory of extended multiphonon electron transitions” [2–4] “for the description of optical spectra of polymethine dyes and J-aggregates using quantum chemistry”. A recent publication by the same authors [5] “demonstrates the feasibility and applicability of the theory of extended multiphonon electron transitions for the description of nonlinear optical properties of polymethine dyes using quantum chemistry and model calculations”. About twenty years have passed since the first publications on the theory of extended multiphonon electron transitions [2–4], however, apart from the author of this theory and this paper, only Petrenko and Stein managed to use their results constructively, despite their promising character [1,5,6], and despite the fact that for a long time, the new theory has been constantly in the field of view of a sufficiently large number of researchers (see, e.g., [7–31]). The low demand in practice for the new, promising theory is associated not only with its complexity (however, we note that this theory is the simplest theory of all its likely future and more complex modifications [6]), but also with an insufficiently clear presentation of its physical foundations in the author’s pioneering works [2–4].
    [Show full text]
  • Near-Infrared Spectroscopic Analysis for Classification
    CORE Metadata, citation and similar papers at core.ac.uk Provided by Wood and Fiber Science (E-Journal) NEAR-INFRARED SPECTROSCOPIC ANALYSIS FOR CLASSIFICATION OF WATER MOLECULES IN WOOD BY A THEORY OF WATER MIXTURES Sang-Yun Yang Graduate Research Assistant Department of Forest Sciences Seoul National University Seoul, Korea 151-921 E-mail: [email protected] Chang-Deuk Eom Research Scientist Korea Forest Research Institute Seoul, Korea E-mail: [email protected] Yeonjung Han PhD Candidate E-mail: [email protected] Yoonseong Chang Graduate Research Assistant E-mail: [email protected] Yonggun Park Department of Forest Sciences Seoul National University Seoul, Korea 151-921 E-mail: [email protected] Jun-Jae Lee Professor E-mail: [email protected] Joon-Weon Choi Associate Professor E-mail: [email protected] Hwanmyeong Yeo*{ Associate Professor Research Institute for Agriculture and Life Sciences Department of Forest Sciences Seoul National University Seoul, Korea, 151-921 E-mail: [email protected] (Received May 2013) * Corresponding author { SWST member Wood and Fiber Science, 46(2), 2014, pp. 138-147 # 2014 by the Society of Wood Science and Technology Yang et al—NIR SPECTROSCOPIC ANALYSIS FOR WOOD WATER MOLECULES 139 Abstract. This study was conducted to analyze the mechanism of moisture adsorption–desorption in wood using near-IR (NIR) spectroscopy. NIR spectra reflected from moist wood were acquired, and spectra in the range from 1800-2100 nm, which were sensitive to water variation, were decomposed into three different components according to the Buijs and Choppin theory. It is assumed that the three components represent three types of bound water: water molecules without -OH groups engaged in hydrogen bonds (S0), water molecules with one -OH group engaged in a hydrogen bond (S1), and water molecules with two -OH groups engaged in hydrogen bonds (S2).
    [Show full text]
  • DOCTOR of PHILOSOPHY Xueyu Song
    Probing properties of glassy water and other liquids with site selective spectroscopies Nhan Chuong Dang A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Physical Chemistry Program of Study Committee: Ryszard Jankowiak, Co-major Professor Klaus Schmidt-Rohr, Co-major Professor Mark Gordon Xueyu Song Victor S.-Y. Lin Iowa State University Ames, Iowa 2005 Copyright 0Nhan Chuong Dang, 2005. All rights reserved. Graduate College Iowa State University This is to certify that the doctoral dissertation of Nhan Chuong Dang has met the dissertation requirements of Iowa State University & SL-%+& Co-major Professor e2z--T6 For the Major Program ... 111 TABLE OF CONTENTS CHAPTER 1. BACKGROUND ON SUPERCOOLED LIQUIDS, GLASSES AND HETEROGENEOUS DYNAMICS 1.1. Formations of Supercooled Liquids and Glasses 1.2. Dynamics, Thermodynamics, and Heterogeneous Dynamics of Supercooled Liquids and Glasses 3 1.3. Background on Supercooled and Glassy water 10 1.4. Remarks on Unsolved Problems Concerning Dynamics of Supercooled Liquids and Glasses and Proposals of Solving the Problems 14 1.5. Dissertation Organization 20 References 22 CHAPTER 2. OPTICAL SPECTROSCOPY OF IMPURITIES IN SOLIDS 27 2.1. Electronic Spectra of Single Impurities in Solids 27 2.2. Electron-Phonon Coupling 33 2.3. Single Site Absorption Line Shape 37 2.4. Inhomogeneous Broadening and Optical Bands of Impurities in Solids 38 2.5. Spectral Hole Burning 42 2.5.1. NPHB Mechanism 47 2.5.2. Dispersive Hole Growth Kinetics 53 2.5.3. Temperature Dependence of Zero-Phonon Hole 56 iv 2.6.
    [Show full text]
  • Broadening of Spectral Lines in Emission of Atomic and Molecular Gases © International Science Press I R a M P ISSN: 2229-3159 8(2), December 2017, Pp
    Broadening of Spectral lines in Emission of Atomic and Molecular Gases © International Science Press I R A M P ISSN: 2229-3159 8(2), December 2017, pp. 99-118 Broadening of Spectral lines in Emission of Atomic and Molecular Gases B. M. SMIRNOV Joint Institute for High Temperatures of Russian Academy of Sciences, Izhorskaya 13/19, Moscow, Russia ABSTRACT: An analogy is shown for broadening the spectral line of atoms in the case of competition between the short-range Doppler broadening mechanism and the long-range broadening mechanism, as well as for the absorption band of a molecular gas in the infrared (IR) spectral range, where a long-range part of the spectrum is also determined by the impact mechanism of the broadening, and the long-range part in the pedestal region the absorption band is associated with the distribution of molecules over the rotational states, and in the region of the wings of the absorption band, it is due to the finite time of collisions involving emitting molecules. The flux of resonance radiation produced by an excited atomic gas is estimated using the concepts of the spectral emission band of a high optical thickness of the gas. These concepts are used for a molecular gas where, in the framework of the regular model (the Elsasser model), expressions are obtained for the absorption coefficient related to a specific spectral absorption band, separately in the pedestal region and for the wings of the absorption band. As a demonstration of the possibilities of these concepts, based on them, the IR radiative flux was calculated on the surface of Venus from its atmosphere, which includes seven vibrational transitions of the carbon dioxide molecule and amounts to 26% of the total flux of IR radiation emitted by the surface of Venus.
    [Show full text]
  • SOLID STATE PHYSICS PART II Optical Properties of Solids
    SOLID STATE PHYSICS PART II Optical Properties of Solids M. S. Dresselhaus 1 Contents 1 Review of Fundamental Relations for Optical Phenomena 1 1.1 Introductory Remarks on Optical Probes . 1 1.2 The Complex dielectric function and the complex optical conductivity . 2 1.3 Relation of Complex Dielectric Function to Observables . 4 1.4 Units for Frequency Measurements . 7 2 Drude Theory{Free Carrier Contribution to the Optical Properties 8 2.1 The Free Carrier Contribution . 8 2.2 Low Frequency Response: !¿ 1 . 10 ¿ 2.3 High Frequency Response; !¿ 1 . 11 À 2.4 The Plasma Frequency . 11 3 Interband Transitions 15 3.1 The Interband Transition Process . 15 3.1.1 Insulators . 19 3.1.2 Semiconductors . 19 3.1.3 Metals . 19 3.2 Form of the Hamiltonian in an Electromagnetic Field . 20 3.3 Relation between Momentum Matrix Elements and the E®ective Mass . 21 3.4 Spin-Orbit Interaction in Solids . 23 4 The Joint Density of States and Critical Points 27 4.1 The Joint Density of States . 27 4.2 Critical Points . 30 5 Absorption of Light in Solids 36 5.1 The Absorption Coe±cient . 36 5.2 Free Carrier Absorption in Semiconductors . 37 5.3 Free Carrier Absorption in Metals . 38 5.4 Direct Interband Transitions . 41 5.4.1 Temperature Dependence of Eg . 46 5.4.2 Dependence of Absorption Edge on Fermi Energy . 46 5.4.3 Dependence of Absorption Edge on Applied Electric Field . 47 5.5 Conservation of Crystal Momentum in Direct Optical Transitions . 47 5.6 Indirect Interband Transitions .
    [Show full text]
  • A Sensitivity Study of the 4.8 M Carbon Dioxide Absorption Band In
    remote sensing Letter A Sensitivity Study of the 4.8 µm Carbon Dioxide Absorption Band in the MWIR Spectral Range Vito Romaniello *, Claudia Spinetti , Malvina Silvestri and Maria Fabrizia Buongiorno Istituto Nazionale di Geofisica e Vulcanologia, Roma 00143, Italy; [email protected] (C.S.); [email protected] (M.S.); [email protected] (M.F.B.) * Correspondence: [email protected] Received: 29 October 2019; Accepted: 27 December 2019; Published: 3 January 2020 Abstract: The measurements of gas concentrations in the atmosphere are recently developed thanks to the availability of gases absorbing spectral channels in space sensors and strictly depending on the instrument performances. In particular, measuring the sources of carbon dioxide is of high interest to know the distribution, both spatial and vertical, of this greenhouse gas and quantify the natural/anthropogenic sources. The present study aims to understand the sensitivity of the CO2 absorption band at 4.8 µm to possibly detect and measure the spatial distribution of emissions from point sources (i.e., degassing volcanic plumes, fires, and industrial emissions). With the aim to define the characteristics of future multispectral imaging space radiometers, the performance of the CO2 4.8 µm absorption band was investigated. Simulations of the “Top of Atmosphere” (TOA) radiance have been performed by using real input data to reproduce realistic scenarios on a volcanic high elevation point source (>2 km): actual atmospheric background of CO2 (~400 ppm) and vertical atmospheric profiles of pressure, temperature, and humidity obtained from probe balloons. The sensitivity of the channel to the CO2 concentration has been analyzed also varying surface temperatures as environmental conditions from standard to high temperature.
    [Show full text]
  • Molecular and Atomic Spectroscopy
    MOLECULAR AND ATOMIC SPECTROSCOPY 1. General Background on Molecular Spectroscopy 3 1.1. Introduction 3 1.2. Beer’s Law 5 1.3. Instrumental Setup of a Spectrophotometer 12 1.3.1. Radiation Sources 13 1.3.2. Monochromators 18 1.3.3. Detectors 20 2. Ultraviolet/Visible Absorption Spectroscopy 23 2.1. Introduction 23 2.2. Effect of Conjugation 28 2.3. Effect of Non-bonding Electrons 34 2.4. Effect of Solvent 37 2.5. Applications 39 2.6. Evaporative Light Scattering Detection 41 3. Molecular Luminescence 42 3.1. Introduction 42 3.2. Energy States and Transitions 42 3.3. Instrumentation 49 3.4. Excitation and Emission Spectra 50 3.5. Quantum Yield of Fluorescence 52 3.6. Variables that Influence Fluorescence Measurements 54 3.7. Other Luminescent Methods 60 4. Infrared Spectroscopy 62 4.1. Introduction 62 4.2. Specialized Infrared Methods 65 4.3. Fourier-Transform Infrared Spectroscopy 68 5. Raman Spectroscopy 73 6. Atomic Spectroscopy 79 6.1. Introduction 79 6.2. Atomization sources 80 6.2.1. Flames 80 6.2.2. Electrothermal Atomization – Graphite Furnace 83 6.2.3. Specialized Atomization Methods 85 6.2.4. Inductively Coupled Plasma 86 6.2.5. Arcs and Sparks 89 1 6.3. Instrument Design Features of Atomic Absorption Spectrophotometers 89 6.3.1. Source Design 89 6.3.2. Interference of Flame Noise 92 6.3.3. Spectral Interferences 94 6.4. Other Considerations 95 6.4.1. Chemical Interferences 95 6.4.2. Accounting for Matrix Effects 96 2 1. GENERAL BACKGROUND ON MOLECULAR SPECTROSCOPY 1.1.
    [Show full text]
  • Relationship Between Absorption Intensity and Fluorescence Lifetime of Molecules S
    Relationship between Absorption Intensity and Fluorescence Lifetime of Molecules S. J. Strickler and Robert A. Berg Citation: J. Chem. Phys. 37, 814 (1962); doi: 10.1063/1.1733166 View online: http://dx.doi.org/10.1063/1.1733166 View Table of Contents: http://jcp.aip.org/resource/1/JCPSA6/v37/i4 Published by the American Institute of Physics. Additional information on J. Chem. Phys. Journal Homepage: http://jcp.aip.org/ Journal Information: http://jcp.aip.org/about/about_the_journal Top downloads: http://jcp.aip.org/features/most_downloaded Information for Authors: http://jcp.aip.org/authors Downloaded 13 May 2012 to 139.18.118.45. Redistribution subject to AIP license or copyright; see http://jcp.aip.org/about/rights_and_permissions THE JOURNAL OF CHEMICAL PHYSICS VOLUME 3;, ~UMBER 4 AUGUST 15,1962 Relationship between Absorption Intensity and Fluorescence Lifetime of Molecules* S. ]. STRICKLER AND ROBERT A. BERG Department of Chemistry and Lawrence Radiation Laboratory, University of California, Berkeley, California (Received March 12, 1962) The equations usually given relating fluorescence lifelime to absorption intensity are strictly applicable only to atomic systems, whose transitions are sharp lines. This p3.per gives the derivation of a modified formula l/ro= 2.880X 10-9 n'(vr)A,-l(!(I/g,,) fEd lnv, which should be valid for broad molecular bands when the transition is strongly allowed. Lifetimes calculated by this for;nula have been comp3.rd with measure:llifeti~e5 for a number of organic molecules in solution. In most cases the values agree within experi nental error, indicating that the formula is valid for such systems.
    [Show full text]
  • Electronic Band Structure of Copper Zinc Tin Sulphide (Cu2znsns4)
    IOSR Journal of Applied Physics (IOSR-JAP) e-ISSN: 2278-4861.Volume 11, Issue 2 Ser. II (Mar. – Apr. 2019), PP 74-81 www.iosrjournals.org Electronic Band Structure of Copper Zinc Tin Sulphide (Cu2ZnSnS4). 1Nwachuku D.N. &2Omehe N.N 1. Physics department, College of Education, Agbor Delta State, Nigeria. 2. Physics department, Federal University, Otuoke, Bayelsa State, Nigeria. Corresponding Author: Nwachuku D.N Abstract: Cu2ZnSnS4 (CZTS), made entirely of abundant materials, has attracted a great interest due to its potential applications in sustainable thin-film solar cell devices. The electronic band structure of kesterite Cu2ZnSnS4 compound has been calculated using the pseudo-potential method. Projector augmented waves (PAW) within the density functional theory (DFT) was used in all calculations using local density approximation (LDA) for one calculation and inclusion of potential correlation term, U to LDA (i.e LDA + U) in another calculation. The results predicted Cu2ZnSnS4 to be a p-type semiconductor with bandgap value for (1) LDA as 0.039 eV and (2) LDA + U as 1.83 eV. This bandgap value of 1.83 eV is in agreement with experimental results and it confirmed the material as a good absorber layer for solar cells. The density of states (DOS) showed that the conduction band was mainly contributions from Sn-5p and Zn-4s orbitals. It is recommended that the orbital independent term, U be added to LDA during calculations because it improves the bandgap value. Keyword: Cu2ZnSnS4, band structure, band gap, density of states. ----------------------------------------------------------------------------------------------------------------------------- ---------- Date of Submission: 27-03-2019 Date of acceptance: 11-04-2019 --------------------------------------------------------------------------------------------------------------------------------------------------- I.
    [Show full text]
  • RADIATION the Fundamentals of Electromagnetic Radiation Principles
    RADIATION The Fundamentals of Electromagnetic Radiation Principles Contents 1. Physics of radiation. 2. Interaction of light with matter. 3. Rayleigh and Mie scattering. 4. Laws of radiation and their implication for radiative processes on earth and its environment. 5. UV radiation and Ozone depletion problem. Physics of Radiation 1. Transport of Radiant Energy (EMW): Electromagnetic radiation is a form of energy derived from oscillating magnetic and electrostatic fields and is capable of transmission through empty space where its velocity is equal to speed of light. 2. Radiation Environment: Almost all the energy for physical and biological processes at the earth’s surface comes from the sun and much of environmental physics is concerned with ways in which this energy is dispersed or stored in thermal, mechanical, or chemical form. Electromagnetic Radiation (i) Electromagnetic Radiation: consists of waves of electric and magnetic energy moving together through space. (ii) All electromagnetic radiation can be classified by frequency from the extremely low to extremely high frequencies. (iii) Extremely high frequency radiation such as Ultraviolet (UV) and X-rays is called “Ionizing Radiation” because it is powerful enough to effect changes in the atoms of matter it strikes, by breaking chemical bonds (ionization) , thus altering their chemical and biological nature. (iv) Electromagnetic radiation at those frequencies below the UV band are generally classified as “Non-Ionizing Radiation” because they typically lack the energy to effect
    [Show full text]
  • Phonon Side Bands of Specular Optical Transitions in Molecular
    Mol. Cryst. Li9. Cryst.. 1977. Vol. 43, pp. 203-222 @ Gordon and Breach Science Publishers, Ltd., 1977 Printed in Holland Phonon Side Bands of Specular Optical Transitions in Molecular Crystals K. P. MELETOV and E. F. SHEKA Institute of Solid State Physics of the Academy of Sciences of the USSR. Chernogolovka, 142432, USSR (Raceiwd October 14, 1976: infrnul form Februury 3. 1977) Quantitative investigations of phonon side bands (PSB) in the small radious centers absorption and luminescence spectra of some impurity molecular crystals are presented. Three pairs of Downloaded By: [HEAL-Link Consortium] At: 15:59 14 January 2008 specular spectra were considered corresponding to three impurity systems: benzene-do in benzene-d6, phenol in benzene-do and /j-methylnaphthalene-d, in naphthalene-d, . Analysis of the observed spectra revealed such PSB regularities. I) The most common characteristic of PSB spectra is the deviation of the PSB shape from specular symmetry. 2) The non-specularness of the PSB shape does not depend on whether the PSB integral intensities are equal or different. 3) There is an unambiguous correlation between the expression of the PSB non-specularness and the temperature variation of the phononless band half width and shift. 4) For weak transitions. the non-specularness of the PSB integral intensities is observed in addition to the PSB shape non-specularness. For the first time the observed characteristics were explained quantitatively in terms of the deviation from the Condon approximation on the basis of one-phonon spectra substracted from the PSB observed. INTRO D U CTlON Much attention has been given recently to the investigation of electron- phonon interaction in small radius centres (SRC) of molecular crystals.
    [Show full text]
  • Chapter 3 Absorption, Emission, Reflection, And
    CHAPTER 3 ABSORPTION, EMISSION, REFLECTION, AND SCATTERING 3.1 Absorption and Emission As noted earlier, blackbody radiation represents the upper limit to the amount of radiation that a real substance may emit at a given temperature. At any given wavelength λ, emissivity is defined as the ratio of the actual emitted radiance, Rλ, to that from an ideal blackbody, Bλ, ελ = Rλ / Bλ . Emissivity is a measure of how strongly a body radiates at a given wavelength; it ranges between zero and one for all real substances. A gray body is defined as a substance whose emissivity is independent of wavelength. In the atmosphere, clouds and gases have emissivities that vary rapidly with wavelength. The ocean surface has near unit emissivity in the visible regions. For a body in local thermodynamic equilibrium the amount of thermal energy emitted must be equal to the energy absorbed; otherwise the body would heat up or cool down in time, contrary to the assumption of equilibrium. In an absorbing and emitting medium in which Iλ is the incident spectral radiance, the emitted spectral radiance Rλ is given by Rλ = ελBλ = aλIλ , where aλ represents the absorptance at a given wavelength. If the source of radiation is in thermal equilibrium with the absorbing medium, then Iλ = Bλ , so that ελ = aλ . This is often referred to as Kirchhoff's Law. In qualitative terms, it states that materials that are strong absorbers at a given wavelength are also strong emitters at that wavelength; similarly weak absorbers are weak emitters. 3.2 Conservation of Energy Consider a layer of absorbing medium where only part of the total incident radiation Iλ is absorbed, and the remainder is either transmitted through the layer or reflected from it (see Figure 3.1).
    [Show full text]