1/28/2013. The Nuclear Age. X-Rays. Discovery of X-Rays. What are X-Rays? Applications. Production of X-Rays

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1 The Nuclear Age X-Rays Radioactivity Decay Processes Discovery of X-Rays 1895 Production of X-Rays What are X-Rays? Applications X-Rays first x-ray picture Discovery of X-Rays Production of X-Rays What are X-Rays? X-ray room X-ray set up High energy photons E = h f = h c / Applications X-ray pictures of patient bodies Customers and baggage check at airports History of art Crystallography Astronomy Sun Earth What did he swallow? What did she swallow? X-ray penetration depends on density of material. Comet Binary System Red Star and Black Hole 1

Satellite X-Ray Detector Radioactivity Discovery of Radioactivity 1896 Types of

photons detection rate Discovery of Radioactivity Types of Radiation Henri Becquerel

Pierre and Marie Curie 1898 Discovery of polonium and radium Spontaneous emission of

Radiation Penetrating Power Type of Radiation Separation in a Magnetic Field Emitted

electrons / positrons -e / +e Medium (few cm of Al) Gamma photons 0 High (several cm of

m N A / molar mass 1. Consider a sample of a thousand 14 6C nuclei.

(c) What is the activity when the sample is 2.00x10 3

(a) What is the number of radioactive nuclei at t = 0?

2 Satellite X-Ray Detector Radioactivity Discovery of Radioactivity 1896 Types of Radiation Decay Rate and Half-Life number of x-ray photons energy of x-ray photons photons detection rate Discovery of Radioactivity Types of Radiation Henri Becquerel 1896 Uranium salts darken a photographic plate covered to exclude light Radioactivity Pierre and Marie Curie 1898 Discovery of polonium and radium Spontaneous emission of nuclear radiation (particles and em radiation) from radionuclides. Radiation Penetrating Power Type of Radiation Separation in a Magnetic Field Emitted Particles Charge Penetrating Power Alpha Helium nuclei 4 He +2e Low (paper) Beta electrons / positrons -e / +e Medium (few cm of Al) Gamma photons 0 High (several cm of Pb) Decay Rate and Half-Life N(t) = N 0 e - t R(t) = R 0 e - t R = N T 1/2 = ln 2 / N = m N A / molar mass 1. Consider a sample of a thousand 14 6C nuclei. How many will still be undecayed in years? 2. (a) What is the decay constant of Ra? (b) If a sample contains 3.00x Ra nuclei at t = 0, what is its activity in Curies at that time? (c) What is the activity when the sample is 2.00x10 3 year old? 3. At time t = 0, a radioactive sample contains 3.50 g of pure 11 6C. (a) What is the number of radioactive nuclei at t = 0? (b) What is the activity of the sample initially and after 8.00 h? 4. A sample of the isotope 131 I, which has a half-life of 8.04 days, has an activity of 5.00 mci at the time of shipment. Upon receipt in a medical laboratory, the activity is 4.20 mci. How much time has elapsed between the two measurements? 2

Decay Processes Disintegration Energy (Q value) Disintegration Energy Alpha Decay Beta Decay Electron Capture Gamma Decay Energy-Level

Alpha Decay (a) What is the Q value? (b) Demonstrate that Q K (c) What is K?

nucleus Y: daughter nucleus Y and He: products of the decay Alpha Decay and Quantum Tunnelling Kinetic Energy of Alpha Particles and

3 Decay Processes Disintegration Energy (Q value) Disintegration Energy Alpha Decay Beta Decay Electron Capture Gamma Decay Energy-Level Diagrams Decays and Nuclide Chart Decay Series Energy released during a nuclear decay Q = (M i M f ) c 2 Nuclear Decays Alpha Decay Radium Alpha Decay (a) What is the Q value? (b) Demonstrate that Q K (c) What is K? A radioactive nucleus emits an alpha particle (loses two protons and two neutrons) A Z X A-4 Z-2Y + 4 2He Q = (M X M Y M ) c 2 X: parent nucleus Y: daughter nucleus Y and He: products of the decay Alpha Decay and Quantum Tunnelling Kinetic Energy of Alpha Particles and Half-Life Radionuclide Q K Half-Life 238U 4.25 MeV 4.5 x 10 9 yr 228U 6.81 MeV 9.1 min The alpha particle tunnels through the barrier, escaping the nucleus. Higher-energy alpha particles come from nuclei with shorter half-lives. 3

4 Discrete Energies of Alpha Particles Alpha Decay Application: The Smoke Detector Polonium 210 Discovery and Characteristics Discovery and Characteristics Applications and Commercial Products Well-known Poisoning Cases Applications and Commercial Products Well-known Poisoning Cases Neutron source for neutron triggers in nuclear reactors and nuclear weapons. Kept Russian Moon rovers internal components warm during lunar nights in the 70 s Anti-static brushes Tobacco Seafood 2006 Alexander Litvinenko 2012 Yasser Arafat Lunokhod 1 Dror Sadeh 1993 Irène Joliot-Curie

The Poisoning of Alexander Litvinenko The Radioactive Death of

antineutrino or neutrino (a) Calculate of the activity of the

(c) Write the equation of the 210 Po alpha decay.

A Z X A Z+1Y + e - + anti e Q = (M X M Y ) c 2 A Z X A Z-1Y + e

and the Neutrino Neutrinos Pauli Nobel Prize 1945 Reines Nobel

Canada SNO (Sudbury Neutrino Observatory) Interact very weakly

5 The Poisoning of Alexander Litvinenko The Radioactive Death of a Russian Spy Beta Decay 1 g of 210 Po was injected in Litvinenko s body. A nucleus decays by emitting an electron or a positron and an antineutrino or neutrino (a) Calculate of the activity of the sample. (b) Compare to activity of class sample (0.1 Ci). (c) Write the equation of the 210 Po alpha decay. (d) Justify the use of 210 Po for the injection. A Z X A Z+1Y + e - + anti e Q = (M X M Y ) c 2 A Z X A Z-1Y + e + + e Q = (M X M Y 2 m é ) c 2 Beta Decay, Conservation Laws and the Neutrino Neutrinos Pauli Nobel Prize 1945 Reines Nobel Prize 1995 One of world s biggest neutrino detector is in Canada SNO (Sudbury Neutrino Observatory) Interact very weakly with matter q =0 m 0. Proposed by Pauli in 1930, first detected by Reines in Beta Decay Application: Carbon Dating 14 N + n 14 C + p 14 C 14 N + e - + anti 5

14 C / 12 C for all living organisms is 1.3 X 10-12 A piece of charcoal containing 25.

The sample shows a 14 C activity of 250 decays/min.

Electron Capture or K-Capture Gamma Decay A nucleus captures one of its orbital

A Z X + 0-1e A Z-1Y + Q = (M X M Y ) c 2 E K A Z X * A ZX + A nucleus undergoes alpha

6 14 C / 12 C for all living organisms is 1.3 X A piece of charcoal containing 25.0 g of carbon is found in some ruins of an ancient city. The sample shows a 14 C activity of 250 decays/min. How long has the tree from which this charcoal came been dead? Electron Capture or K-Capture Gamma Decay A nucleus captures one of its orbital electron (K-shell). A Z X + 0-1e A Z-1Y + Q = (M X M Y ) c 2 E K A Z X * A ZX + A nucleus undergoes alpha or beta decay and is left in an excited state. The nucleus undergoes a second decay to a lower energy state by emitting gamma rays. Energy-Level Diagrams Summary Decay Pathways Beta-minus decay Gamma decay 12 5 B 12 6C* + e - + anti 12 6 C* 12 6C + 6

Decays and Nuclide Chart Identify the missing particle(s)

Series Our environment is constantly replenished with

7 Decays and Nuclide Chart Identify the missing particle(s) X 1) 45 Ca X + e - + anti 2) 58 Cu * X + 3) 46 Cr 46 V + X 4) 234 Pu X + 5) 239 Np 239 Pa + X 6) X + 4 He 24 Mg + n 7) 235 U + n 90 Sr + X + 2 n 8) 2 1 H 2 H + X Decay Series Our environment is constantly replenished with radioactive elements produced by the three natural decay series. 7

Chapter 3 Radioactivity

Chapter 3 Radioactivity Marie Curie 1867 1934 Discovered new radioactive elements Shared Nobel Prize in physics in 1903 Nobel Prize in Chemistry in 1911 Radioactivity Radioactivity is the spontaneous emission