DOCSLIB.ORG

The Spectrum of Atomic Hydrogen

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Spectrum of Atomic Hydrogen The Spectrum of Atomic Hydrogen For almost a century light emitted by the simplest of atoms has been the chief experimental basis for theories of the structure of matter. Exploration of the hydrogen spectrum continues, now aided by lasers by Theodor W. Hansch, Arthur L. Schawlow and George W. Series he spectrum of the hydrogen atom sorbed. glvmg rise to dark lines on a that he could account for the positions has proved to be the Rosetta stone bright background. of all the known lines by applying a sim­ Tof modern physics: once this pat­ Hydrogen is the simplest of atoms. be­ ple empirical formula. The entire set of tern of lines had been deciphered much ing made up of a single electron and a lines has since come to be known as the else could also be understood. Most no­ nucleus that consists of a single proton. Balmer series. Another group of lines. tably. it was largely the effort to explain and so it can be expected to have the the Lyman series. lies in the far ultravio­ the spectrum of light emitted by the hy­ simplest spectrum. The spectrum is not. let. and there are other series at longer drogen atom that inspired the laws of however. an easy one to record. The wavelengths. Within each series the in­ quantum mechanics. Those laws have most prominent line was detected in dividual lines are designated by Greek since been found to apply not only to 1853 by Anders Jonas Angstrom. (The letters. starting with the line of longest the hydrogen atom but also to other common unit for measuring wave­ wavelength. Thus the bright red line first atoms. to molecules and to matter in lengths of light is named for Angstrom; seen by Angstrom is the Balmer-alpha bulk. They are the ultimate foundation one angstrom unit is equal to 10.8 centi­ line. the next is the Balmer-beta line and of modern chemistry. of solid-state meter.) In the next two decades three so on. Because of the prominence of the physics and even of applied sciences more lines were observed. but the first Balmer-alpha line it is sometimes called such as electronics. extended series of atomic-hydrogen The central position of the hydrogen lines was found not in the laboratory but atom in the history of 20th-century in the spectra of stars. In 1881. working physics might seem to suggest that the with the first photographs of stellar spectrum has long been known in all its spectra. Sir William Huggins identified BALMER-ALPHA 6.563 details. That is not so. Only in the past 10 lines as being emissions of atomic few years have some of the subtler fea­ hydrogen. tures of the spectrum been resolved. and It may seem surprising that lines of many others have not yet been observed the hydrogen spectrum were seen in directly. Measuring the positions of the astronomical observations before they spectral lines remains today a significant were seen in terrestrial experiments. The test of the' predictions of the quantum difficulty in measuring the spectrum in theory. the laboratory is not in detecting the The most recent advances in the anal­ lines but in preparing pure atomic hy­ ysis of the spectrum can be attributed to drogen. Ordinary hydrogen gas consists a new tool of spectroscopy: the laser. of diatomic molecules (H2). which have Beca use the finest details of the spec­ a spectrum that is much more compli­ trum are closely spaced they can be dis-I cated than the spectrum of the isolated tinguished only by light that is highly hydrogen atom. Splitting the molecules monochromatic. or confined to a nar­ requires more energy than can be sup­ row range of wavelengths. The laser is a plied by most thermal excitations. such source of such light. As a result of some as a flame. One device that furnishes ingenious laboratory technology it has the energy very effectively is the gas­ become a spectroscopic instrument of discharge tube. where electrons accel­ unprecedented resolution. erated by an applied voltage dissociate the molecules. Over the years means The Line Spectrum have been discovered for enhancing the atomic spectrum and suppressing When light from a hot filament is dis­ the molecular one. persed according to wavelength by a The spectral lines detected by Hug­ prism or a diffraction grating. the result gins range in wavelength from the red is a continuous fan of colors. but the portion of the visible spectrum to the spectrum from a pure. rarefied gas of near ultraviolet. The first two lines are PATTERN OF DISTINCT LINES is formed atoms or molecules consists of discrete quite far apart. but the subsequent ones when the light emitted by hydrogen atoms is lines. If the spectrum is recorded from come at smoothly decreasing intervals. dispersed according to wavelength. The lines are those of the Balmer series, and their ap­ light emitted by the gas. it appears as a and those at the shortest wavelengths proximate wavelengths are given in angstrom sequence of bright lines against a dark are bunched closely together. In 1885. units (one angstrom is equal to 10.8 centime­ background. If light is passed through working from the astronomical mea­ ter). The color photograph was made by Jon the gas. discrete wavelengths are ab- surements. Johann Jakob Balmer found Brenneis and one of the authors (Schawlow) 94 © 1979 SCIENTIFIC AMERICAN, INC simply the hydrogen-alpha, or H-alpha, hydrogen atom the equation has a sim­ of. he said, as being like the notes of a line. pler form: piano, whose tones depend in a compli­ In 1889 Johannes Rydberg discovered cated way on the structure of the instru­ that the line spectra of many elements, ment as a whole. most notably those of the alkali metals, The reference to musical notes was could be fitted by a single empirical for­ not an idle one. In the 19th century mula. A later version of the formula, When the appropriate values of m and n many investigators had speculated that which is equivalent to Rydberg's equa­ are substituted in this formula, it yields the light emitted by atoms might be un­ tion but more explicit, has the form the wavelengths of all the lines in the derstood by some analogy to the modes hydrogen spectrum. of vibration of a solid body. The pres­ 1 1 ence of multiple lines in each series R r - I-j . X = L(m + b)2 (n + C)2 Atomic Struc;:ture could then be explained by assuming that the first line was the fundamental Here A (the Greek letter lambda) is the In 1912 Niels Bohr spent most of the mode and the rest were overtones, or wavelength of a particular line in an year at the University of Manchester harmonics. No optical spectrum could atomic spectrum, m and n are numbers working in the laboratory of Ernest be resolved into a fundamental frequen­ that take on successive integer values (1, Rutherford, who had just made a vi­ cy and its overtones, however, and so 2, 3 and so on) and R, band c are con­ tal contribution to the understanding of more direct examination of the atom it­ stants. The values of band c depend on atomic structure. By then the Balmer self was undertaken. what series of lines is being measured, and the Rydberg formulas were well Rutherford's contribution was the but R is the same for all lines of all the known to spectroscopists, and they had demonstration that the atom is not a elements. R is now called the Rydberg been thoroughly tested, but Bohr had solid body but rather consists of a constant; if the wavelength is expressed never heard of either of them. When he small, dense, positively charged nucleus in meters, R has the value (097 X 107 was told of Balmer's equation, he was and the requisite number of negatively and the dimensions of reciprocal me­ able to derive it almost immediately charged electrons to form a stable and ters. After Rydberg had checked his for­ from the properties of the hydrogen electrically neutral system. Bohr under­ mula against a number of spectra he atom. Abraham Pais and T. D. Lee have took to explain the spectra of atoms in wrote: "I had just finished testing vari­ reported that Bohr was asked late in his the context of this model. In doing so he ous forms of the function when I heard life how he could have escaped knowing risked the ridicule of his contemporaries of Mr. Balmer's communication on the of the Balmer formula. He explained by hypothesizing that within the atom spectral lines of atomic hydrogen. I was that in those days most physicists re­ the established laws of physics do not delighted to find that his formula is a garded atomic spectra as being so com­ apply. Those laws predicted that any special case of mine, with the same val­ plicated they were hardly a part of fun­ bound electron would radiate away all ue of R, and with c = 0." Hence for the damental physics. They were thought its energy and fall into the nucleus. Bohr WAVELENGTH (ANGSTROM UNITS) BALMER-BETA BALMER-GAMMA BALMER-DELTA 4,861 4,340 4,102 in the latter's laboratory at Stanford University, The black-and­ charge tube in which hydrogen molecules (H2) are dissociated into white spectrnm was recorded in 1927 by Gerhard Herzberg, who was atoms by an electric potential, In the color photograph the yellow and then at the Darmstadt Technical University in Germany, The inter­ green bands and the continuous blue background at the right are not vals between the lines are different in the two photographs because part of the atomic-hydrogen spectrum but result from molecular con­ Brenneis and Schawlow dispersed the light with a diffraction grating, taminants in the discharge tube.
Load more

Recommended publications
  • Glossary Physics (I-Introduction)
    1 Glossary Physics (I-introduction) - Efficiency: The percent of the work put into a machine that is converted into useful work output; = work done / energy used [-]. = eta In machines: The work output of any machine cannot exceed the work input (<=100%); in an ideal machine, where no energy is transformed into heat: work(input) = work(output), =100%. Energy: The property of a system that enables it to do work. Conservation o. E.: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. Equilibrium: The state of an object when not acted upon by a net force or net torque; an object in equilibrium may be at rest or moving at uniform velocity - not accelerating. Mechanical E.: The state of an object or system of objects for which any impressed forces cancels to zero and no acceleration occurs. Dynamic E.: Object is moving without experiencing acceleration. Static E.: Object is at rest.F Force: The influence that can cause an object to be accelerated or retarded; is always in the direction of the net force, hence a vector quantity; the four elementary forces are: Electromagnetic F.: Is an attraction or repulsion G, gravit. const.6.672E-11[Nm2/kg2] between electric charges: d, distance [m] 2 2 2 2 F = 1/(40) (q1q2/d ) [(CC/m )(Nm /C )] = [N] m,M, mass [kg] Gravitational F.: Is a mutual attraction between all masses: q, charge [As] [C] 2 2 2 2 F = GmM/d [Nm /kg kg 1/m ] = [N] 0, dielectric constant Strong F.: (nuclear force) Acts within the nuclei of atoms: 8.854E-12 [C2/Nm2] [F/m] 2 2 2 2 2 F = 1/(40) (e /d ) [(CC/m )(Nm /C )] = [N] , 3.14 [-] Weak F.: Manifests itself in special reactions among elementary e, 1.60210 E-19 [As] [C] particles, such as the reaction that occur in radioactive decay.
    [Show full text]
  • Or Continuous Spectrum and Not to the Line Spectra. in the X-Ray Region, In
    662 PHYSICS: W. D UA NE PROC. N. A. S. intensity is greatest close to -80 and that it falls off regularly as the angle departs therefrom. We conclude, therefore, that the momentum of the electron in its orbit uithin the atom does not affect the direction of ejection in the way denanded by the theory of Auger and Perrin. While this does not constitute definite evidence against the physical reality of electronic orbits, it is a serious difficulty for the conception. A detailed discussion of the general question here raised in the light of new experimental results will be published elsewhere. 1 Auger, P., J. Physique Rad., 8, 1927 (85-92). 2 Loughridge, D. H., in press. 3 Bothe, W., Zs. Physik, 26, 1924 (59-73). 4 Auger, P., and Perrin, F., J. Physique Rad., 8, 1927 (93-111). 6 Bothe, W., Zs. Physik, 26,1924 (74-84). 6 Watson, E. C., in press. THE CHARACTER OF THE GENERAL, OR CONTINUOUS SPEC- TRUM RADIA TION By WILLIAM DuANX, DJPARTMSNT OF PHysIcs, HARVARD UNIVERSITY Communicated August 6, 1927 The impacts of electrons against atoms produce two different kinds of radiation-the general, or continuous spectrum and the line spectra. By far the greatest amount of energy radiated belongs to the general, or continuous spectrum and not to the line spectra. In the X-ray region, in particular, the continuous, or general radiation spectrum carries most of the radiated energy. In spite of this, and because the line spectra have an important bearing on atomic structure, the general radiation has received much less attention than the line spectra in the recent de- velopment of fundamental ideas in physical science.
    [Show full text]
  • Discrete-Continuous and Classical-Quantum
    Under consideration for publication in Math. Struct. in Comp. Science Discrete-continuous and classical-quantum T. Paul C.N.R.S., D.M.A., Ecole Normale Sup´erieure Received 21 November 2006 Abstract A discussion concerning the opposition between discretness and continuum in quantum mechanics is presented. In particular this duality is shown to be present not only in the early days of the theory, but remains actual, featuring different aspects of discretization. In particular discreteness of quantum mechanics is a key-stone for quantum information and quantum computation. A conclusion involving a concept of completeness linking dis- creteness and continuum is proposed. 1. Discrete-continuous in the old quantum theory Discretness is obviously a fundamental aspect of Quantum Mechanics. When you send white light, that is a continuous spectrum of colors, on a mono-atomic gas, you get back precise line spectra and only Quantum Mechanics can explain this phenomenon. In fact the birth of quantum physics involves more discretization than discretness : in the famous Max Planck’s paper of 1900, and even more explicitly in the 1905 paper by Einstein about the photo-electric effect, what is really done is what a computer does: an integral is replaced by a discrete sum. And the discretization length is given by the Planck’s constant. This idea will be later on applied by Niels Bohr during the years 1910’s to the atomic model. Already one has to notice that during that time another form of discretization had appeared : the atomic model. It is astonishing to notice how long it took to accept the atomic hypothesis (Perrin 1905).
    [Show full text]
  • Group Problems #22 - Solutions
    Group Problems #22 - Solutions Friday, October 21 Problem 1 Ritz Combination Principle Show that the longest wavelength of the Balmer series and the longest two wavelengths of the Lyman series satisfy the Ritz Combination Principle. The wavelengths corresponding to transitions between two energy levels in hydrogen is given by: n2 λ = λlimit 2 2 ; (1) n − n0 where n0 = 1 for the Lyman series, n0 = 2 for the Balmer series, and λlimit = 91:1 nm for the Lyman series and λlimit = 364:5 nm for the Balmer series. Inspection of this equation shows that the longest wavelength corresponds to the transition between n = n0 and n = n0 + 1. Thus, for the Lyman series, the longest two wavelengths are λ12 and λ13. For the Balmer series, the longest wavelength is λ23. The Ritz combination principle states that certain pairs of observed frequencies from the hydrogen spectrum add together to give other observed frequencies. For this particular problem, we then have: ν12 + ν23 = ν13 =) h(ν12 + ν23) = hν13 (2) 1 1 1 =) hc + = hc (3) λ12 λ23 λ13 1 1 1 =) + = : (4) λ12 λ23 λ13 Inverting Eqn. 1 above gives: 2 2 2 1 1 n − n0 1 n0 = 2 = 1 − 2 : (5) λ λlimit n λlimit n To calculate 1/λ12 and 1/λ13, we use the Lyman series numbers and find 1/λ12 = −1 −1 3=(4 ∗ 91:1) = 0:00823 nm and 1/λ13 = 8=(9 ∗ 91:1) = 0:00976 nm . To compute 1/λ23, we use the Balmer series numbers and find 1/λ23 = 5=(9 ∗ 364:5) = 0:00152 −1 nm .
    [Show full text]
  • The Balmer Series
    The Balmer Series Introduction Historically, the spectral lines of hydrogen have been categorized as six distinct series. The visible portion of the hydrogen spectrum is contained in the Balmer series, named after Johann Balmer who discovered an empirical relationship for calculating its wave- lengths [2]. In 1885 Balmer discovered that by labeling the four visible lines of the hydorgen spectrum with integers n, (n = 3, 4, 5, 6) (See Table 1 and Figure 1) each wavelength λ could be calculated from the relationship n2 λ = B , (1) n2 − 4 where B = 364.56 nm. Johannes Rydberg generalized Balmer’s result to include all of the wavelengths of the hydrogen spectrum. The Balmer formula is more commonly re–expressed in the form of the Rydberg formula 1 1 1 = RH − , (2) λ 22 n2 where n =3, 4, 5 . and the Rydberg constant RH =4/B. The purpose of this experiment is to determine the wavelengths of the visible spec- tral lines of hydrogen using a spectrometer and to calculate the Balmer constant B. Procedure The spectrometer used in this experiment is shown in Fig. 1. Adjust the diffraction grating so that the normal to its plane makes a small angle α to the incident beam of light. This is shown schematically in Fig. 2. Since α u 0, the angles between the first and zeroth order intensity maxima on either side, θ and θ0 respectively, are related to the wavelength λ of the incident light according to [1] λ = d sin(φ) , (3) accurate to first order in α. Here, d is the separation between the slits of the grating, and θ0 + θ φ = (4) 2 1 Color Wavelength [nm] Integer [n] Violet2 410.2 6 Violet1 434.0 5 blue 486.1 4 red 656.3 3 Table 1: The wavelengths and integer associations of the visible spectral lines of hy- drogen shown in Fig.
    [Show full text]
  • Physics of the Atom
    Physics of the Atom Ernest The Nobel Prize in Chemistry 1908 Rutherford "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances" Niels Bohr The Nobel Prize in Physics 1922 "for his services in the investigation of the structure of atoms and of the radiation emanating from them" W. Ubachs – Lectures MNW-1 Early models of the atom atoms : electrically neutral they can become charged positive and negative charges are around and some can be removed. popular atomic model “plum-pudding” model: W. Ubachs – Lectures MNW-1 Rutherford scattering Rutherford did an experiment that showed that the positively charged nucleus must be extremely small compared to the rest of the atom. Result from Rutherford scattering 2 dσ ⎛ 1 Zze2 ⎞ 1 = ⎜ ⎟ ⎜ ⎟ 4 dΩ ⎝ 4πε0 4K ⎠ sin ()θ / 2 Applet for doing the experiment: http://www.physics.upenn.edu/courses/gladney/phys351/classes/Scattering/Rutherford_Scattering.html W. Ubachs – Lectures MNW-1 Rutherford scattering the smallness of the nucleus the radius of the nucleus is 1/10,000 that of the atom. the atom is mostly empty space Rutherford’s atomic model W. Ubachs – Lectures MNW-1 Atomic Spectra: Key to the Structure of the Atom A very thin gas heated in a discharge tube emits light only at characteristic frequencies. W. Ubachs – Lectures MNW-1 Atomic Spectra: Key to the Structure of the Atom Line spectra: absorption and emission W. Ubachs – Lectures MNW-1 The Balmer series in atomic hydrogen The wavelengths of electrons emitted from hydrogen have a regular pattern: Johann Jakob Balmer W. Ubachs – Lectures MNW-1 Lyman, Paschen and Rydberg series the Lyman series: the Paschen series: W.
    [Show full text]
  • Lecture #2: August 25, 2020 Goal Is to Define Electrons in Atoms
    Lecture #2: August 25, 2020 Goal is to define electrons in atoms • Bohr Atom and Principal Energy Levels from “orbits”; Balance of electrostatic attraction and centripetal force: classical mechanics • Inability to account for emission lines => particle/wave description of atom and application of wave mechanics • Solutions of Schrodinger’s equation, Hψ = Eψ Required boundaries => quantum numbers (and the Pauli Exclusion Principle) • Electron configurations. C: 1s2 2s2 2p2 or [He]2s2 2p2 Na: 1s2 2s2 2p6 3s1 or [Ne] 3s1 => Na+: [Ne] Cl: 1s2 2s2 2p6 3s23p5 or [Ne]3s23p5 => Cl-: [Ne]3s23p6 or [Ar] What you already know: Quantum Numbers: n, l, ml , ms n is the principal quantum number, indicates the size of the orbital, has all positive integer values of 1 to ∞(infinity) (Bohr’s discrete orbits) l (angular momentum) orbital 0s l is the angular momentum quantum number, 1p represents the shape of the orbital, has integer values of (n – 1) to 0 2d 3f ml is the magnetic quantum number, represents the spatial direction of the orbital, can have integer values of -l to 0 to l Other terms: electron configuration, noble gas configuration, valence shell ms is the spin quantum number, has little physical meaning, can have values of either +1/2 or -1/2 Pauli Exclusion principle: no two electrons can have all four of the same quantum numbers in the same atom (Every electron has a unique set.) Hund’s Rule: when electrons are placed in a set of degenerate orbitals, the ground state has as many electrons as possible in different orbitals, and with parallel spin.
    [Show full text]
  • HI Balmer Jump Temperatures for Extragalactic HII Regions in the CHAOS Galaxies
    HI Balmer Jump Temperatures for Extragalactic HII Regions in the CHAOS Galaxies A Senior Thesis Presented in Partial Fulfillment of the Requirements for Graduation with Research Distinction in Astronomy in the Undergraduate Colleges of The Ohio State University By Ness Mayker The Ohio State University April 2019 Project Advisors: Danielle A. Berg, Richard W. Pogge Table of Contents Chapter 1: Introduction ............................... 3 1.1 Measuring Nebular Abundances . 8 1.2 The Balmer Continuum . 13 Chapter 2: Balmer Jump Temperature in the CHAOS galaxies .... 16 2.1 Data . 16 2.1.1 The CHAOS Survey . 16 2.1.2 CHAOS Balmer Jump Sample . 17 2.2 Balmer Jump Temperature Determinations . 20 2.2.1 Balmer Continuum Significance . 20 2.2.2 Balmer Continuum Measurements . 21 + 2.2.3 Te(H ) Calculations . 23 2.2.4 Photoionization Models . 24 2.3 Results . 26 2.3.1 Te Te Relationships . 26 − 2.3.2 Discussion . 28 Chapter 3: Conclusions and Future Work ................... 32 1 Abstract By understanding the observed proportions of the elements found across galaxies astronomers can learn about the evolution of life and the universe. Historically, there have been consistent discrepancies found between the two main methods used to measure gas-phase elemental abundances: collisionally excited lines and optical recombination lines in H II regions (ionized nebulae around young star-forming regions). The origin of the discrepancy is thought to hinge primarily on the strong temperature dependence of the collisionally excited emission lines of metal ions, principally Oxygen, Nitrogen, and Sulfur. This problem is exacerbated by the difficulty of measuring ionic temperatures from these species.
    [Show full text]
  • Observations of the Lyman Series Forest Towards the Redshift 7.1 Quasar ULAS J1120+0641 R
    A&A 601, A16 (2017) Astronomy DOI: 10.1051/0004-6361/201630258 & c ESO 2017 Astrophysics Observations of the Lyman series forest towards the redshift 7.1 quasar ULAS J1120+0641 R. Barnett1, S. J. Warren1, G. D. Becker2, D. J. Mortlock1; 3; 4, P. C. Hewett5, R. G. McMahon5; 6, C. Simpson7, and B. P. Venemans8 1 Astrophysics Group, Blackett Laboratory, Imperial College London, London SW7 2AZ, UK e-mail: [email protected] 2 Department of Physics & Astronomy, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA 3 Department of Mathematics, Imperial College London, London SW7 2AZ, UK 4 Department of Astronomy, Stockholm University, Albanova, 10691 Stockholm, Sweden 5 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 6 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 7 Gemini Observatory, Northern Operations Center, N. A’ohoku Place, Hilo, HI 96720, USA 8 Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany Received 15 December 2016 / Accepted 9 February 2017 ABSTRACT We present a 30 h integration Very Large Telescope X-shooter spectrum of the Lyman series forest towards the z = 7:084 quasar ULAS J1120+0641. The only detected transmission at S=N > 5 is confined to seven narrow spikes in the Lyα forest, over the redshift range 5:858 < z < 6:122, just longward of the wavelength of the onset of the Lyβ forest. There is also a possible detection of one further unresolved spike in the Lyβ forest at z = 6:854, with S=N = 4:5.
    [Show full text]
  • Rydberg Constant and Emission Spectra of Gases
    Page 1 of 10 Rydberg constant and emission spectra of gases ONE WEIGHT RECOMMENDED READINGS 1. R. Harris. Modern Physics, 2nd Ed. (2008). Sections 4.6, 7.3, 8.9. 2. Atomic Spectra line database https://physics.nist.gov/PhysRefData/ASD/lines_form.html OBJECTIVE - Calibrating a prism spectrometer to convert the scale readings in wavelengths of the emission spectral lines. - Identifying an "unknown" gas by measuring its spectral lines wavelengths. - Calculating the Rydberg constant RH. - Finding a separation of spectral lines in the yellow doublet of the sodium lamp spectrum. INSTRUCTOR’S EXPECTATIONS In the lab report it is expected to find the following parts: - Brief overview of the Bohr’s theory of hydrogen atom and main restrictions on its application. - Description of the setup including its main parts and their functions. - Description of the experiment procedure. - Table with readings of the vernier scale of the spectrometer and corresponding wavelengths of spectral lines of hydrogen and helium. - Calibration line for the function “wavelength vs reading” with explanation of the fitting procedure and values of the parameters of the fit with their uncertainties. - Calculated Rydberg constant with its uncertainty. - Description of the procedure of identification of the unknown gas and statement about the gas. - Calculating resolution of the spectrometer with the yellow doublet of sodium spectrum. INTRODUCTION In this experiment, linear emission spectra of discharge tubes are studied. The discharge tube is an evacuated glass tube filled with a gas or a vapor. There are two conductors – anode and cathode - soldered in the ends of the tube and connected to a high-voltage power source outside the tube.
    [Show full text]
  • Bohr's Theory and Spectra of Hydrogen And
    ____________________________________________________________________________________________________ Subject Chemistry Paper No and Title 8 and Physical Spectroscopy Module No and Title 7 and Bohr’s theory and spectra of hydrogen and hydrogen- like ions. Module Tag CHE_P8_M7 CHEMISTRY PAPER No. : 8 (PHYSICAL SPECTROSCOPY) MODULE No. : 7 (BOHR’S THEORY AND SPECTRA OF HYDROGEN AND HYDROGEN-LIKE IONS) ____________________________________________________________________________________________________ TABLE OF CONTENTS 1. Learning Outcomes 2. What is a Spectrum? 2.1 Introduction 2.2 Atomic Spectra 2.3 Hydrogen Spectrum 2.4 Balmer Series 2.5 The Rydberg Formula 3. Bohr’s Theory 3.1 Bohr Model 3.2 Line Spectra 3.3 Multi-electron Atoms 4. Summary CHEMISTRY PAPER No. : 8 (PHYSICAL SPECTROSCOPY) MODULE No. : 7 (BOHR’S THEORY AND SPECTRA OF HYDROGEN AND HYDROGEN-LIKE IONS) ____________________________________________________________________________________________________ 1. Learning Outcomes After studying this module, you should be able to grasp the important ideas of Bohr’s Theory of the structure of atomic hydrogen. We will first review the experimental observations of the atomic spectrum of hydrogen, which led to the birth of quantum mechanics. 2. What is a Spectrum? 2.1 Introduction In spectroscopy, we are interested in the absorption and emission of radiation by matter and its consequences. A spectrum is the distribution of photon energies coming from a light source: • How many photons of each energy are emitted by the light source? Spectra are observed by passing light through a spectrograph: • Breaks the light into its component wavelengths and spreads them apart (dispersion). • Uses either prisms or diffraction gratings. The absorption and emission of photons are governed by the Bohr condition ΔE = hν.
    [Show full text]
  • Spectroscopy and the Stars
    SPECTROSCOPY AND THE STARS K H h g G d F b E D C B 400 nm 500 nm 600 nm 700 nm by DR. STEPHEN THOMPSON MR. JOE STALEY The contents of this module were developed under grant award # P116B-001338 from the Fund for the Improve- ment of Postsecondary Education (FIPSE), United States Department of Education. However, those contents do not necessarily represent the policy of FIPSE and the Department of Education, and you should not assume endorsement by the Federal government. SPECTROSCOPY AND THE STARS CONTENTS 2 Electromagnetic Ruler: The ER Ruler 3 The Rydberg Equation 4 Absorption Spectrum 5 Fraunhofer Lines In The Solar Spectrum 6 Dwarf Star Spectra 7 Stellar Spectra 8 Wien’s Displacement Law 8 Cosmic Background Radiation 9 Doppler Effect 10 Spectral Line profi les 11 Red Shifts 12 Red Shift 13 Hertzsprung-Russell Diagram 14 Parallax 15 Ladder of Distances 1 SPECTROSCOPY AND THE STARS ELECTROMAGNETIC RADIATION RULER: THE ER RULER Energy Level Transition Energy Wavelength RF = Radio frequency radiation µW = Microwave radiation nm Joules IR = Infrared radiation 10-27 VIS = Visible light radiation 2 8 UV = Ultraviolet radiation 4 6 6 RF 4 X = X-ray radiation Nuclear and electron spin 26 10- 2 γ = gamma ray radiation 1010 25 10- 109 10-24 108 µW 10-23 Molecular rotations 107 10-22 106 10-21 105 Molecular vibrations IR 10-20 104 SPACE INFRARED TELESCOPE FACILITY 10-19 103 VIS HUBBLE SPACE Valence electrons 10-18 TELESCOPE 102 Middle-shell electrons 10-17 UV 10 10-16 CHANDRA X-RAY 1 OBSERVATORY Inner-shell electrons 10-15 X 10-1 10-14 10-2 10-13 10-3 Nuclear 10-12 γ 10-4 COMPTON GAMMA RAY OBSERVATORY 10-11 10-5 6 4 10-10 2 2 -6 4 10 6 8 2 SPECTROSCOPY AND THE STARS THE RYDBERG EQUATION The wavelengths of one electron atomic emission spectra can be calculated from the Use the Rydberg equation to fi nd the wavelength ot Rydberg equation: the transition from n = 4 to n = 3 for singly ionized helium.
    [Show full text]