DOCSLIB.ORG

Nuclear Binding Energy and Nuclear Stability

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nuclear Binding Energy and Nuclear Stability Chapter 1: Radioactivity Chapter 1: Radioactivity 35 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Radioactivity • Radioactivity is defined as the spontaneous nuclear transformation that results in the formation of new elements. • Radioactivity and radioactive properties of nuclide are determined by nuclear considerations and independent of chemical and physical states of the radioisotope. • The probability of radioactive transformation depends primarily on two factors: ‐ Nuclear stability as related to the neutron‐to‐proton ratio. ‐ The mass‐energy relationship among the parent nucleus, daughter nucleus and the emitted particles. 36 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity The Origin of Nuclear Radiation and a Few Related Concepts • Nuclear force and Coulomb barrier. • Nuclear binding energy and nuclear stability. • Nucleartransformationasawaytoachievegreaternuclear stability and associated energy release. 37 NPRE 441, Principles of Radiation Protection Nuclear Forces Within the incredibly small nuclear size （～10‐15m）,thetwostrongest forces in nature, Coulomb force and strong nuclear force, are pitted against each other. When the balance is broken, the resultant radioactivity yields particles of enormous energy. Coulomb potenital 1 q1 q2 VC , where 0 is the electrical permitivity http://230nsc1.phy‐astr.gsu.edu/hbase/hframe.html 40 r 38 NPRE 441, Principles of Radiation Protection Potential Energy of Nucleus • Nucleons are bounded together in nucleus by the strong force, which has a short range of ~10‐15m. • The strong force is powerful enough to overcome the Coulomb repulsion between the positively charged protons. Coulomb potenital 1 q1 q2 VC , where 0 is the electrical permitivity 40 r 39 NPRE 441, Principles of Radiation Protection Coulomb Barrier 40 NPRE 441, Principles of Radiation Protection Coulomb Barrier We can use the following equation to estimate the radiuses of the Cl nucleus and the proton, R 1.3A1/3 1015 m With A=1 and A=35 for the proton and the Cl nucleus, we have 1 q q 1 2 , V C 40 r where 0 is the electrical permitivity 41 NPRE 441, Principles of Radiation Protection A Simple Nuclear Reaction For example, thermal neutron capture by hydrogen nucleus. 42 NPRE 441, Principles of Radiation Protection Mass Defect and Nuclear Binding Energy In this case, the energy transition due to the mass defect is 43 NPRE 441, Principles of Radiation Protection Nuclear Binding Energy The nuclear binding energy In this case, the binding energy for the deuterium nucleus is given by 44 NPRE 441, Principles of Radiation Protection Nuclear Binding Energy • Nuclei are made up of protons and neutron, but the mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it. • This difference is a measure of the nuclear binding energy, which holds the nucleus together. The binding energy can be calculated from the Einstein relationship: Nuclear binding energy = Δmc2 The nuclear binding energy 45 Nuclear Binding Energy • Binding energy is always positive. • The average binding energy per nucleon peaks for A = 40 to 120, with a maximum of ~8.5MeV. • It then drops off for either higher or lower A. • There are a few nuclei, 4He, 12C and 16Oatthelowermass number end that have binding energies (per nucleon) well above that for adjacent nuclei. • In fact, these nuclei are all “multiples” of the alpha particle. •And… 46 NPRE 441, Principles of Radiation Protection Fission Reactions • A fission reaction splits up a large nucleus into smaller pieces. • A fission reaction typically happens when a neutron hits a nucleus with enough energy to make the nucleus unstable. 47 NPRE 441, Principles of Radiation Protection Average Binding Energy Per Nucleon Comparing Fusion and Fission Reactions http://230nsc1.phy‐astr.gsu.edu/hbase/hframe.html 48 NPRE 441, Principles of Radiation Protection Binding Energy of Atoms http://230nsc1.phy‐astr.gsu.edu/hbase/hframe.html 49 NPRE 441, Principles of Radiation Protection Z Chart of the Nuclides (177, 117) The nuclides are the possible nuclei of atoms. Z determines the chemistry, because the neutral atom with the nuclide as its nucleus has Zelectrons. Half‐life N Source: http://www.nndc.bnl.gov/chart/reZoom.jsp?newZoom=5 50 Chart of the Nuclides Be11 β- 11.5, 9.4 γ 2.1 51 Nuclear Stability and the Origin of Radioactivity Secondary radiations, e.g., gamma‐rays, X‐ rays, alpha‐particles, and electrons Alpha decay Parent (Z, N) Daughter (Z‐2, N‐2) 210 206 4 84 Po 82 Pb 2 He Beta decay: Parent (Z, N) Daughter (Z+1, N‐1) → ̅ Parent (Z, N) Daughter (Z‐1, N+1) Positron decay: → Electron capture: A A Z X e Z 1Y 22 22 0 11 Na10 Ne1 52 Chapter 1: Radioactivity Take‐Home Points Covered in Today’s Lecture Introduction • Major sources of radiation dose to the general population a. Medical dose b. Dose from radioactive background (ranked by importance) i. Internal ingestion of radioactivity ii. Space and cosmogenic radiation iii. Terrestrial naturally occurring radioactive materials (NORM) c. Radiation dose from indoor radon i. Inhaled radioactive Rn isotopes form the uranium (Rn‐222), thorium (Rn‐220), and actinium series (Rn219) ii. Alpha particles emitted by Rn‐222 and its daughters Chapter 1: Radioactivity • Nuclear binding energy a. What is nuclear binding energy? b. Calculation of binding energy for given radionuclides • Understanding the Chart of Nuclides a. Stable and non‐stable nuclides b. Energy release from radioactive decay 53 Chapter 1: Radioactivity Alpha Decay Key concepts • Coulomb barrier and energy release through alpha decay. • Energy spectrum of alpha particles. • Major health hazards related to alpha emission 54 NPRE 441, Principles of Radiation Protection Average Binding Energy Per Nucleon 55 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Alpha Emission • An alpha particle is a highly energetic helium nucleus consisting of two neutrons and 2 protons. • It is normally emitted from isotopes when the neutron‐ to‐proton ratio is too low – called the alpha decay. • Atomic number and atomic mass number are conserved in alpha decays 56 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Alpha Decay –An Example •Half‐life: 138.376 days; Decay mode: alpha‐decay (branching ratio: 100%); Energy release: 5.407MeV • 210Po has a neutron‐to‐proton ratio of 126 to 84 (1.5:1) and 206Pb has a neutron‐to‐proton ratio of 124 to 82 (~1.51:1) increased neutron‐to‐ proton ratio. • Alpha decay is also accompanied by the loss of two orbital electrons. 57 NPRE 441, Principles of Radiation Protection Nuclear Stability and the Origin of Radioactivity Secondary radiations, e.g., gamma‐rays, X‐ rays, alpha‐particles, and electrons Alpha decay Parent (Z, N) Daughter (Z‐2, N‐2) 210 206 4 84 Po 82 Pb 2 He Beta decay: Parent (Z, N) Daughter (Z+1, N‐1) → ̅ Parent (Z, N) Daughter (Z‐1, N+1) Positron decay: → Electron capture: A A Z X e Z 1Y 22 22 0 11 Na10 Ne1 58 Nuclear Binding Energy The nuclear binding energy In this case, the binding energy for the deuterium nucleus is given by 59 NPRE 441, Principles of Radiation Protection Potential Energy of Nucleus • Nucleons are bounded together in nucleus by the strong force, which has a short range of ~10‐15m. • The strong force is powerful enough to overcome the Coulomb repulsion between the positively charged protons. Coulomb potenital 1 q1 q2 VC , where 0 is the electrical permitivity 40 r 60 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Alpha Emission In heavy elements, It would require a minimum kinetic energy of ~3.8MeV for the alpha particle to “tunneling through” the potential well … 61 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Alpha Decay With only a few exceptions (Samarium‐147), naturally occurring alpha decay are found only among elements of atomic number greater than 82 because of the following reasons: • Electrostatic repulsive force in heavy nuclei increases much more rapidly with the increasing atomic number than the cohesive nuclear force. The magnitude of the electrostatic repulsive force may closely approach or even exceed that of the nuclear force. • Emitted alpha particles must have sufficiently high kinetic energy to overcome the potential barrier resultant from the strong nuclear force. 62 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Energy Release from Alpha Decay An example: Alpha decay of 226Ra The energy release can be found using the data shown in the table previously used for deriving binding energy 63 NPRE 441, Principles of Radiation Protection Understanding the Mass Defect and Nuclear Binding Energy 64 Chapter 1: Radioactivity Energy Release in Alpha Emission A more accurate version The required kinetic energy has to come from the decrease in mass following the decay process. The relationship between mass and energy associated with an alpha emission is given as 65 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Energy Release from Alpha Decay An example: Alpha decay of 226Ra The same example, when considering the daughter atom to have two less electrons, Note: Md, Md: masses of the parent and daughter atoms What is the energy of the alpha particle? 66 NPRE 441, Principles of Radiation Protection Chapter 1: Radioactivity Energy Spectra of Alpha Particles m is the mass of the alpha particle, and M is the mass of the recoil nucleus. Measured energy spectrum of alpha particles emitted from the decay of 238Pu. NPRE 441, Principles of Radiation Protection 67 Chapter 1: Radioactivity Energy Spectra of Alpha Particles Alpha decays are sometimes accompanied by the excited daughter products which complicates the resultant alpha particle spectra. The kinetic energy of alpha particles is given by E QA 4 / A, where A is the atomic mass number of the parent nucleus and Q is the energy release.
Load more

Recommended publications
  • Probing Pulse Structure at the Spallation Neutron Source Via Polarimetry Measurements
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2017 Probing Pulse Structure at the Spallation Neutron Source via Polarimetry Measurements Connor Miller Gautam University of Tennessee, Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Nuclear Commons Recommended Citation Gautam, Connor Miller, "Probing Pulse Structure at the Spallation Neutron Source via Polarimetry Measurements. " Master's Thesis, University of Tennessee, 2017. https://trace.tennessee.edu/utk_gradthes/4741 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Connor Miller Gautam entitled "Probing Pulse Structure at the Spallation Neutron Source via Polarimetry Measurements." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Physics. Geoffrey Greene, Major Professor We have read this thesis and recommend its acceptance: Marianne Breinig, Nadia Fomin Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Probing Pulse Structure at the Spallation Neutron Source via Polarimetry Measurements A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Connor Miller Gautam May 2017 c by Connor Miller Gautam, 2017 All Rights Reserved.
    [Show full text]
  • CHEM 1412. Chapter 21. Nuclear Chemistry (Homework) Ky
    CHEM 1412. Chapter 21. Nuclear Chemistry (Homework) Ky Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. Consider the following statements about the nucleus. Which of these statements is false? a. The nucleus is a sizable fraction of the total volume of the atom. b. Neutrons and protons together constitute the nucleus. c. Nearly all the mass of an atom resides in the nucleus. d. The nuclei of all elements have approximately the same density. e. Electrons occupy essentially empty space around the nucleus. ____ 2. A term that is used to describe (only) different nuclear forms of the same element is: a. isotopes b. nucleons c. shells d. nuclei e. nuclides ____ 3. Which statement concerning stable nuclides and/or the "magic numbers" (such as 2, 8, 20, 28, 50, 82 or 128) is false? a. Nuclides with their number of neutrons equal to a "magic number" are especially stable. b. The existence of "magic numbers" suggests an energy level (shell) model for the nucleus. c. Nuclides with the sum of the numbers of their protons and neutrons equal to a "magic number" are especially stable. d. Above atomic number 20, the most stable nuclides have more protons than neutrons. e. Nuclides with their number of protons equal to a "magic number" are especially stable. ____ 4. The difference between the sum of the masses of the electrons, protons and neutrons of an atom (calculated mass) and the actual measured mass of the atom is called the ____. a. isotopic mass b.
    [Show full text]
  • Nuclear Models: Shell Model
    LectureLecture 33 NuclearNuclear models:models: ShellShell modelmodel WS2012/13 : ‚Introduction to Nuclear and Particle Physics ‘, Part I 1 NuclearNuclear modelsmodels Nuclear models Models with strong interaction between Models of non-interacting the nucleons nucleons Liquid drop model Fermi gas model ααα-particle model Optical model Shell model … … Nucleons interact with the nearest Nucleons move freely inside the nucleus: neighbors and practically don‘t move: mean free path λ ~ R A nuclear radius mean free path λ << R A nuclear radius 2 III.III. ShellShell modelmodel 3 ShellShell modelmodel Magic numbers: Nuclides with certain proton and/or neutron numbers are found to be exceptionally stable. These so-called magic numbers are 2, 8, 20, 28, 50, 82, 126 — The doubly magic nuclei: — Nuclei with magic proton or neutron number have an unusually large number of stable or long lived nuclides . — A nucleus with a magic neutron (proton) number requires a lot of energy to separate a neutron (proton) from it. — A nucleus with one more neutron (proton) than a magic number is very easy to separate. — The first exitation level is very high : a lot of energy is needed to excite such nuclei — The doubly magic nuclei have a spherical form Nucleons are arranged into complete shells within the atomic nucleus 4 ExcitationExcitation energyenergy forfor magicm nuclei 5 NuclearNuclear potentialpotential The energy spectrum is defined by the nuclear potential solution of Schrödinger equation for a realistic potential The nuclear force is very short-ranged => the form of the potential follows the density distribution of the nucleons within the nucleus: for very light nuclei (A < 7), the nucleon distribution has Gaussian form (corresponding to a harmonic oscillator potential ) for heavier nuclei it can be parameterised by a Fermi distribution.
    [Show full text]
  • A Measurement of the 2 Neutrino Double Beta Decay Rate of 130Te in the CUORICINO Experiment by Laura Katherine Kogler
    A measurement of the 2 neutrino double beta decay rate of 130Te in the CUORICINO experiment by Laura Katherine Kogler A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Physics in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Stuart J. Freedman, Chair Professor Yury G. Kolomensky Professor Eric B. Norman Fall 2011 A measurement of the 2 neutrino double beta decay rate of 130Te in the CUORICINO experiment Copyright 2011 by Laura Katherine Kogler 1 Abstract A measurement of the 2 neutrino double beta decay rate of 130Te in the CUORICINO experiment by Laura Katherine Kogler Doctor of Philosophy in Physics University of California, Berkeley Professor Stuart J. Freedman, Chair CUORICINO was a cryogenic bolometer experiment designed to search for neutrinoless double beta decay and other rare processes, including double beta decay with two neutrinos (2νββ). The experiment was located at Laboratori Nazionali del Gran Sasso and ran for a period of about 5 years, from 2003 to 2008. The detector consisted of an array of 62 TeO2 crystals arranged in a tower and operated at a temperature of ∼10 mK. Events depositing energy in the detectors, such as radioactive decays or impinging particles, produced thermal pulses in the crystals which were read out using sensitive thermistors. The experiment included 4 enriched crystals, 2 enriched with 130Te and 2 with 128Te, in order to aid in the measurement of the 2νββ rate. The enriched crystals contained a total of ∼350 g 130Te. The 128-enriched (130-depleted) crystals were used as background monitors, so that the shared backgrounds could be subtracted from the energy spectrum of the 130- enriched crystals.
    [Show full text]
  • Lecture 22 Alpha Decay 1 Introduction 2 Fission and Fusion
    Nuclear and Particle Physics - Lecture 22 Alpha decay 1 Introduction We have looked at gamma decays (due to the EM force) and beta decays (due to the weak force) and now will look at alpha decays, which are due to the strong/nuclear force. In contrast to the previous decays which do not change A, alpha decays happen by emission of some of the 4 nucleons from the nucleus. Specifically, for alpha decay, an alpha particle, 2He, is ejected so generically A A−4 4 X − Y + He Z !Z 2 2 for some X and Y . Y clearly has a different number of nucleons to X. Compare how alpha and beta decays move the nuclei around in Z,N plane N β+ β- α Z Note that gamma decays cannot change Z, N or A. 2 Fission and fusion Alpha decay is in fact only one specific case of a whole range of processes which involve emission of nucleons. These range from single proton or neutron emission up to splitting the nucleus into two roughly equal parts. Particularly in the latter case, these are called fission decays. Which nuclei would we expect to fission? The binding energy per nucleon curve shows that 56 the maximum occurs around 26Fe and drops off to either side. Hence, both small A and large A nuclei are less strongly bound per nucleon than medium A. This means there will be some energy release if two small nuclei are combined into a larger one, a process called fusion which will be discussed later in the course.
    [Show full text]
  • Radioactive Decay
    North Berwick High School Department of Physics Higher Physics Unit 2 Particles and Waves Section 3 Fission and Fusion Section 3 Fission and Fusion Note Making Make a dictionary with the meanings of any new words. Einstein and nuclear energy 1. Write down Einstein’s famous equation along with units. 2. Explain the importance of this equation and its relevance to nuclear power. A basic model of the atom 1. Copy the components of the atom diagram and state the meanings of A and Z. 2. Copy the table on page 5 and state the difference between elements and isotopes. Radioactive decay 1. Explain what is meant by radioactive decay and copy the summary table for the three types of nuclear radiation. 2. Describe an alpha particle, including the reason for its short range and copy the panel showing Plutonium decay. 3. Describe a beta particle, including its range and copy the panel showing Tritium decay. 4. Describe a gamma ray, including its range. Fission: spontaneous decay and nuclear bombardment 1. Describe the differences between the two methods of decay and copy the equation on page 10. Nuclear fission and E = mc2 1. Explain what is meant by the terms ‘mass difference’ and ‘chain reaction’. 2. Copy the example showing the energy released during a fission reaction. 3. Briefly describe controlled fission in a nuclear reactor. Nuclear fusion: energy of the future? 1. Explain why nuclear fusion might be a preferred source of energy in the future. 2. Describe some of the difficulties associated with maintaining a controlled fusion reaction.
    [Show full text]
  • Arxiv:1901.01410V3 [Astro-Ph.HE] 1 Feb 2021 Mental Information Is Available, and One Has to Rely Strongly on Theoretical Predictions for Nuclear Properties
    Origin of the heaviest elements: The rapid neutron-capture process John J. Cowan∗ HLD Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019, USA Christopher Snedeny Department of Astronomy, University of Texas, 2515 Speedway, Austin, TX 78712-1205, USA James E. Lawlerz Physics Department, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706-1390, USA Ani Aprahamianx and Michael Wiescher{ Department of Physics and Joint Institute for Nuclear Astrophysics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556, USA Karlheinz Langanke∗∗ GSI Helmholtzzentrum f¨urSchwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany and Institut f¨urKernphysik (Theoriezentrum), Fachbereich Physik, Technische Universit¨atDarmstadt, Schlossgartenstraße 2, 64298 Darmstadt, Germany Gabriel Mart´ınez-Pinedoyy GSI Helmholtzzentrum f¨urSchwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany; Institut f¨urKernphysik (Theoriezentrum), Fachbereich Physik, Technische Universit¨atDarmstadt, Schlossgartenstraße 2, 64298 Darmstadt, Germany; and Helmholtz Forschungsakademie Hessen f¨urFAIR, GSI Helmholtzzentrum f¨urSchwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany Friedrich-Karl Thielemannzz Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland and GSI Helmholtzzentrum f¨urSchwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany (Dated: February 2, 2021) The production of about half of the heavy elements found in nature is assigned to a spe- cific astrophysical nucleosynthesis process: the rapid neutron capture process (r-process). Although this idea has been postulated more than six decades ago, the full understand- ing faces two types of uncertainties/open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experi- arXiv:1901.01410v3 [astro-ph.HE] 1 Feb 2021 mental information is available, and one has to rely strongly on theoretical predictions for nuclear properties.
    [Show full text]
  • Interaction of Neutrons with Matter
    Interaction of Neutrons With Matter § Neutrons interactions depends on energies: from > 100 MeV to < 1 eV § Neutrons are uncharged particles: Þ No interaction with atomic electrons of material Þ interaction with the nuclei of these atoms § The nuclear force, leading to these interactions, is very short ranged Þ neutrons have to pass close to a nucleus to be able to interact ≈ 10-13 cm (nucleus radius) § Because of small size of the nucleus in relation to the atom, neutrons have low probability of interaction Þ long travelling distances in matter See Krane, Segre’, … While bound neutrons in stable nuclei are stable, FREE neutrons are unstable; they undergo beta decay with a lifetime of just under 15 minutes n ® p + e- +n tn = 885.7 ± 0.8 s ≈ 14.76 min Long life times Þ before decaying possibility to interact Þ n physics … x Free neutrons are produced in nuclear fission and fusion x Dedicated neutron sources like research reactors and spallation sources produce free neutrons for the use in irradiation neutron scattering exp. 33 N.B. Vita media del protone: tp > 1.6*10 anni età dell’universo: (13.72 ± 0,12) × 109 anni. beta decay can only occur with bound protons The neutron lifetime puzzle From 2016 Istitut Laue-Langevin (ILL, Grenoble) Annual Report A. Serebrov et al., Phys. Lett. B 605 (2005) 72 A.T. Yue et al., Phys. Rev. Lett. 111 (2013) 222501 Z. Berezhiani and L. Bento, Phys. Rev. Lett. 96 (2006) 081801 G.L. Greene and P. Geltenbort, Sci. Am. 314 (2016) 36 A discrepancy of more than 8 seconds !!!! https://www.scientificamerican.com/article/neutro
    [Show full text]
  • 14. Structure of Nuclei Particle and Nuclear Physics
    14. Structure of Nuclei Particle and Nuclear Physics Dr. Tina Potter Dr. Tina Potter 14. Structure of Nuclei 1 In this section... Magic Numbers The Nuclear Shell Model Excited States Dr. Tina Potter 14. Structure of Nuclei 2 Magic Numbers Magic Numbers = 2; 8; 20; 28; 50; 82; 126... Nuclei with a magic number of Z and/or N are particularly stable, e.g. Binding energy per nucleon is large for magic numbers Doubly magic nuclei are especially stable. Dr. Tina Potter 14. Structure of Nuclei 3 Magic Numbers Other notable behaviour includes Greater abundance of isotopes and isotones for magic numbers e.g. Z = 20 has6 stable isotopes (average=2) Z = 50 has 10 stable isotopes (average=4) Odd A nuclei have small quadrupole moments when magic First excited states for magic nuclei higher than neighbours Large energy release in α, β decay when the daughter nucleus is magic Spontaneous neutron emitters have N = magic + 1 Nuclear radius shows only small change with Z, N at magic numbers. etc... etc... Dr. Tina Potter 14. Structure of Nuclei 4 Magic Numbers Analogy with atomic behaviour as electron shells fill. Atomic case - reminder Electrons move independently in central potential V (r) ∼ 1=r (Coulomb field of nucleus). Shells filled progressively according to Pauli exclusion principle. Chemical properties of an atom defined by valence (unpaired) electrons. Energy levels can be obtained (to first order) by solving Schr¨odinger equation for central potential. 1 E = n = principle quantum number n n2 Shell closure gives noble gas atoms. Are magic nuclei analogous to the noble gas atoms? Dr.
    [Show full text]
  • 1663-29-Othernuclearreaction.Pdf
    it’s not fission or fusion. It’s not alpha, beta, or gamma dosimeter around his neck to track his exposure to radiation decay, nor any other nuclear reaction normally discussed in in the lab. And when he’s not in the lab, he can keep tabs on his an introductory physics textbook. Yet it is responsible for various experiments simultaneously from his office computer the existence of more than two thirds of the elements on the with not one or two but five widescreen monitors—displaying periodic table and is virtually ubiquitous anywhere nuclear graphs and computer codes without a single pixel of unused reactions are taking place—in nuclear reactors, nuclear bombs, space. Data printouts pinned to the wall on the left side of the stellar cores, and supernova explosions. office and techno-scribble densely covering the whiteboard It’s neutron capture, in which a neutron merges with an on the right side testify to a man on a mission: developing, or atomic nucleus. And at first blush, it may even sound deserving at least contributing to, a detailed understanding of complex of its relative obscurity, since neutrons are electrically neutral. atomic nuclei. For that, he’ll need to collect and tabulate a lot For example, add a neutron to carbon’s most common isotope, of cold, hard data. carbon-12, and you just get carbon-13. It’s slightly heavier than Mosby’s primary experimental apparatus for doing this carbon-12, but in terms of how it looks and behaves, the two is the Detector for Advanced Neutron Capture Experiments are essentially identical.
    [Show full text]
  • Nuclear Physics: the ISOLDE Facility
    Nuclear physics: the ISOLDE facility Lecture 1: Nuclear physics Magdalena Kowalska CERN, EP-Dept. [email protected] on behalf of the CERN ISOLDE team www.cern.ch/isolde Outline Aimed at both physics and non-physics students This lecture: Introduction to nuclear physics Key dates and terms Forces inside atomic nuclei Nuclear landscape Nuclear decay General properties of nuclei Nuclear models Open questions in nuclear physics Lecture 2: CERN-ISOLDE facility Elements of a Radioactive Ion Beam Facility Lecture 3: Physics of ISOLDE Examples of experimental setups and results 2 Small quiz 1 What is Hulk’s connection to the topic of these lectures? Replies should be sent to [email protected] Prize: part of ISOLDE facility 3 Nuclear scale Matter Crystal Atom Atomic nucleus Macroscopic Nucleon Quark Angstrom Nuclear physics: femtometer studies the properties of nuclei and the interactions inside and between them 4 and with a matching theoretical effort theoretical a matching with and facilities experimental dedicated many with better and better it know to getting are we but Today Becquerel, discovery of radioactivity Skłodowska-Curie and Curie, isolation of radium : the exact form of the nuclear interaction is still not known, known, not still is interaction of nuclearthe form exact the : Known nuclides Known Chadwick, neutron discovered History 5 Goeppert-Meyer, Jensen, Haxel, Suess, nuclear shell model first studies on short-lived nuclei Discovery of 1-proton decay Discovery of halo nuclei Discovery of 2-proton decay Calculations with
    [Show full text]
  • Spontaneous Fission
    13) Nuclear fission (1) Remind! Nuclear binding energy Nuclear binding energy per nucleon V - Sum of the masses of nucleons is bigger than the e M / nucleus of an atom n o e l - Difference: nuclear binding energy c u n r e p - Energy can be gained by fusion of light elements y g r e or fission of heavy elements n e g n i d n i B Mass number 157 13) Nuclear fission (2) Spontaneous fission - heavy nuclei are instable for spontaneous fission - according to calculations this should be valid for all nuclei with A > 46 (Pd !!!!) - practically, a high energy barrier prevents the lighter elements from fission - spontaneous fission is observed for elements heavier than actinium - partial half-lifes for 238U: 4,47 x 109 a (α-decay) 9 x 1015 a (spontaneous fission) - Sponatenous fission of uranium is practically the only natural source for technetium - contribution increases with very heavy elements (99% with 254Cf) 158 1 13) Nuclear fission (3) Potential energy of a nucleus as function of the deformation (A, B = energy barriers which represent fission barriers Saddle point - transition state of a nucleus is determined by its deformation - almost no deformation in the ground state - fission barrier is higher by 6 MeV Ground state Point of - tunneling of the barrier at spontaneous fission fission y g r e n e l a i t n e t o P 159 13) Nuclear fission (4) Artificially initiated fission - initiated by the bombardment with slow (thermal neutrons) - as chain reaction discovered in 1938 by Hahn, Meitner and Strassmann - intermediate is a strongly deformed
    [Show full text]