History of RadiationThe birth of atomic models: History of Radiation The birth of atomic models NE162 – Lecture 1 Chapter 1 and 2 of text book Jasmina Vujic


At the end of the 19th century, many scientists did not realize they were on the edge of a revolution in physics…: At the end of the 19th century, many scientists did not realize they were on the edge of a revolution in physics… “The most important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote… Our future discoveries must be looked for in the sixth place of the decimals.” -- Albert Michelson, 1894


Radiation Chronicle: Radiation Chronicle 400 B.C. - In Greece, Democritus proclaims all material things are made of tiny particles “atoms”, or “not divisible” 1789 - The element uranium was discovered by Martin Klaproth 1869 - Dmitri Mendeleyev developed the periodic law of elements, which later evolved in the Table of Elelments. 1885 - Balmer publishes an empirical formula that gives the observed wavelength of hydrogen light spectra 1890 - Thorium is first used in mantles for camping lanterns


1895 - Wilhelm Roentgen: 1895 - Wilhelm Roentgen Discovered X-rays on 8th November 1895 The World immediately realised their medical potential Won Nobel Prize in 1901


1896 - Henri Becquerel: 1896 - Henri Becquerel Discovered radioactivity on 26 February 1896 “Some atoms give off energy in form of rays. Uranium gives of radiation.” Shared Nobel Prize in 1903 with P. Curie.


X-rays was quickly put to clinical use: Frau Roentgen’s hand, 1895 X-rays was quickly put to clinical use 1896 (Pupin in New York City): using a screen as well as film for advanced x-ray imaging.


Dr Rome Wagner and assistant: Dr Rome Wagner and assistant


Radiation Chronicle - cont.: Radiation Chronicle - cont. 1897 - J.J. Thomson discovers the electron. 1898 - Marie and Pierre Curie discover the first radioactive elements: radium and polonium. Radioactivity is named by Marie Curie. Marie Won Nobel Prize in 1911 for discovery of radium and polonium. 1899 - Ernest Rutherford concludes that radiation can be divided into two types: alpha and beta rays. Won Nobel Prize in 1908. 1900 - Pierre Curie observes another type of radiation - the gamma rays. Shared Nobel Prize in 1903 with Becquirel. 1905 - Albert Einstein develops the theory about relationship between mass and energy: E = mc2. Won Nobel Prize in 1919 for discovery of photoeffect. 1911 - Ernest Rutherford discovers that most of an atom is empty space and identifies the atomic nucleus 1911 - George de Hevesy conceives the idea of using radio tracers - applied later to medical diagnosis. (Won a Nobel Prize in 1943) 1913 - Niels Bohr introduces the first atom model, the mini solar system.


Radiation Chronicle - cont.: Radiation Chronicle - cont. 1913 - Hans Geiger invents the Geiger counter form measuring radioactivity. 1913 - Frederick Proesher publishes the first study on the intravenous injection of radium for therapy of various diseases. 1920 - Ernest Rutherford discovered and named the proton. 1927 - Herman Blumgart, a Boston physician, first uses radioactive tracers to diagnose heart disease. 1932 - James Chadwick discovers the neutron. Won Nobel Prize in 1935. 1932 - Ernest O. Lawrence and M. Stanley Livingston publish the first article on "the production of high speed light ions without the use of high voltages." It is a milestone in the production of usable quantities of radionuclides. E. Lawrence wan Nobel Prize in 1939 - cyclotron. 1934 - Irene and Frederic Joliot-Curie discover artificial radioactivity. In 1935 - Irene and Frederic Joliot-Curie receive Nobel Prize for creating the first artificial radioactive isotope.


Radiation Chronicle - cont.: Radiation Chronicle - cont. 1935 - Nuclear medicine comes into existance when cyclotron-produced radioisotopes and nuclear radiation becomes available in the U.S. 1936 - John H. Lawrence, the brother of Ernest, makes the first clinical therapeutic application of an artificial radionuclide when he uses phosphorus-32 to treat leukemia. 1937 - John Livingood, Fred Fairbrother and Glenn Seaborg discover iron-59. 1938 John Livingood and Glenn Seaborg discover iodine-131 and cobalt-60 - all isotopes currently used in nuclear medicine. G. Seaborg shared Nobel Prize with MacMillan in 1951. 1938 - Otto Hahn and Fritz Strassman, produce lighter elements by bombarding uranium with neutrons. Irene Joliot-Curie and Pavle Savich notice the same effect. However, it was Lise Meitner and Otto Frisch that recognized it as splitting of the atom - “fission”. O. Hahn won a Nobel Prize in 1944. 1938 - Enrico Fermi won a Nobel Prize forproduction of new elements by neutron irradiation.


Radiation Chronicle - cont.: Radiation Chronicle - cont. 1939 - The principles of a nuclear chain reaction demonstrated. They take a first patent on the production of nuclear energy. The principle of nuclear reactors was first recorded and sealed in an envelope where it remains secret during the WWII. Irene and Frederic Joliot-Curie 1939 - Emilio Segre and Glenn Seaborg discover technetium-99m - an isotope currently used in nuclear medicine. 1939 - U.S. Advisory Committee on Uranium recommends a program to develop an atomic bomb (this is later named the Manhattan Project). 1940 - The Rockefeller Foundation funds the first cyclotron dedicated for biomedical radioisotope production at Washington University in St. Louis. 1942 - The Manhattan Project is formed to secretly build the atomic bomb before the Nazis. 1942 - Fermi demonstrates the first self-sustaining nuclear chain reaction in a lab at the University of Chicago. 1942 - The United States drops atomic bombs on Hiroshima and Nagasaki. Japan surrenders.


First Reports of Injury: First Reports of Injury Late 1896 Elihu Thomson - burns from deliberate exposure of a finger to X-rays Edison’s assistant - hair fell out & scalp became inflamed & ulcerated


Mihran Kassabian (1870-1910) : Mihran Kassabian (1870-1910)


Sister Blandina (1871 - 1916): Sister Blandina (1871 - 1916) 1898, started work as radiographer in Cologne held nervous patients & children with unprotected hands controlled the degree of hardness of the X-ray tube by placing her hand behind of the screen.


Sister Blandina: Sister Blandina After 6 months strong flushing & swellings of hands diagnosed with an X-ray cancer, some fingers amputated then whole hand amputated whole arm amputated. 1915 severed difficulties of breathing extensive shadow on the left side of her thorax large wound on her whole front- and back-side Died on 22nd October 1916.


First Radiotherapy Treatment Emil Herman Grubbé: First Radiotherapy Treatment Emil Herman Grubbé 29 January 1896 woman (50) with breast cancer 18 daily 1-hour irradiation condition was relieved died shortly afterwards from metastases.


William Rollins: William Rollins Rollins W. X-light kills. Boston Med Surg J 1901;144:173. Codman EA. No practical danger from the x-ray. Boston Med Surg J 1901;144:197


Slide19: Early Protective Suit Lead glasses Filters Tube shielding Early personal “dosemeters” etc.


Protection Progress: Protection Progress 1898 Roentgen Society Committee of Inquiry 1915 Roentgen Society publishes recommendations 1921 British X-Ray and Radiation Protection Committee established and issue reports 1928 2nd International Congress of Radiology adopts British recommendations + the Roentgen 1931 USACXRP publishes the first recommendations (0.2 r/d) 1934 4th ICR adopts 0.2 Roentgens per day limit


Life Span Study: Life Span Study About 94,000 persons, > 50% still alive in 1995 By 1991 about 8,000 cancer deaths  430 of these attributable to radiation 21 out of 800 in utero with dose > 10 mSv severely mentally retarded individuals have been identified No increase in hereditary disease http://www.rerf.or.jp/eigo/glossary/lsspopul.htm


Theory came later : Birth of planetary model – Part I: Rutherford: Theory came later : Birth of planetary model – Part I: Rutherford 1900: Alpha, beta and gamma rays are known 1909 Rutherford conclude from bombarding thin gold foils with alpha particles (Po(214-84)): Large angle deflection seen in 1/8000 alpha particles suggests the existence of a very small and massive nucleus Proposed the planetary model We now know: Rnuc ~ 1.3 A1/3 x 10-15 m Ratom ~ 1.5 x 10-10 m


Part II: Bohr’s hydrogen atom - 1913: Part II: Bohr’s hydrogen atom - 1913 Bohr was not satisfied from classical mechanics in the planetary model Unstable model, since an accelerated charge will emit light and therefore lose E Bohr postulates the first semi-classical model Angular momentum of electron is quantized: mvr = nħ Then energy and orbital radii are also quantized (derive radius on the board) rn = 0.529 n2/Z (Å) En = -13.6 Z2/n2 (eV)


Problem with Bohr’s model and classical mechanics: Problem with Bohr’s model and classical mechanics Could only predict correctly the energy levels of H. The dual behavior of light (particle and wave) could not be explained by classical mechanics The approach of Bohr of mixing classical mechanic with quantizing certain variables was suddenly heavily used other accurate predictions were made with new Semi-classical or relativistic models Prelude for Quantum Mechanics


Birth of Quantum Mechanics: 1925: Birth of Quantum Mechanics: 1925 Simultaneously and independently: Heizenberg realized that the reason Bohr’s model failed was that it was trying to predict none observable variables (position, speed) Heizenberg actually created a model focusing on measurable variable: Balm wave length: Showed that Dp.Dx ≥ħ or DE.Dt ≥ħ This is the Heizenberg uncertainty principle, stating that it is impossible to measure precisely the speed and location of a particle Also showed that x.px was different from px.x. Others showed in this a typical matrix property and called Heizenberg model the MATRIX MECHANICS Schroendiger established a law defined by a differential equation that describes matter as a wave (D2X and Dt) Later, Schroendiger equation will be formalized by linear algebra and matrix simplification


Pauli principle: No two electrons in an atom can be in the same state: Pauli principle: No two electrons in an atom can be in the same state Quantization came naturally out of quantum mechanics Four quantum numbers fully described the electron energy levels (derive atomic layer on the board) Principal quantum number : n Describes the orbital shells n=1, 2 and 3 for K, L and M shells respectively Corresponds to Bohr’s angular momentum quantization Azimuthal quantum number: l Fine structure (sommerfeld shows that elliptical orbits in relativity implies this quantization) l = 0, 1, 2, …, n Magnetic quantum number: m An electron orbiting a nucleus is a current that produces a magnetic field affecting the atom magnetic field m = [-l, l] Intrinsic spin of electron: s s = [-1/2, ½]


Slide29: Summary on Atomic Structure Nucleus Contains protons and neutrons Small Size Relatively large mass Extremely large density Large amount of stored energy Orbiting Electrons Large size Low density Orbit nucleus near speed of light Small amount of energy relative to nucleus Responsible for chemical bonds


Slide30: Nomenclature for Elements "X" = Element Symbol "Z" = # Protons Each element has a unique "Z” "N” = # Neutrons Atomic Mass # = "A" "A" = Z + N = # Protons + # Neutrons Isotope: same Z, different N, thus different A X A Z


Continuous and characteristic X-rays: Continuous and characteristic X-rays Roentgen discovered that electron that hit a target produces photons Higher the A of the target, the more efficient the X-ray production Range of energy of photon: [0,E of incident e-]


X-rays production : X-rays production Electron can produce photons in two ways: Slowing down of incident electron when hitting target emits photons with minimum wave length: l = 12400 (Å.eV)/Ee K shell electron of target ejected L e- fills it: Ka M e- fills it: Kb


The Auger electron: The Auger electron Non-radiative phenomenon Incident electron can eject a K shell electron Then and L electron makes a transition to fill K shell vacancy without emitting a photon Instead, this energy leads to the ejection of another L shell electron, leading to two missing electron in the target atom This can trigger a cascade of Auger electrons