History of Radiation The birth of atomic models

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History of RadiationThe birth of atomic models

• NE162 Lecture 1
• Chapter 1 and 2 of text book
• Jasmina Vujic

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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
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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

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1895 - Wilhelm Roentgen

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

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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.

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X-rays was quickly put to clinical use
Frau Roentgens hand, 1895
1896 (Pupin in New York City) using a screen as
well as film for advanced x-ray imaging.
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Dr Rome Wagner and assistant
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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.

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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.

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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.

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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.

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First Reports of Injury

• Late 1896
• Elihu Thomson - burns from deliberate exposure of
  a finger to X-rays

Edisons assistant - hair fell out scalp became
inflamed ulcerated
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Mihran Kassabian (1870-1910)
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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.

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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.

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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.

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William Rollins

• Rollins W. X-light kills. Boston Med Surg J
  1901144173.
• Codman EA. No practical danger from the x-ray.
  Boston Med Surg J 1901144197

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Early Protective Suit

• Lead glasses
• Filters
• Tube shielding
• Early personal dosemeters
• etc.

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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

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Life Span Study

• About 94,000 persons,
• gt 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 gt 10 mSv
  severely mentally retarded individuals have been
  identified
• No increase in hereditary disease
• http//www.rerf.or.jp/eigo/glossary/lsspopul.htm

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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

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Part II Bohrs 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 nh
• 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)

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Problem with Bohrs 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

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Birth of Quantum Mechanics 1925

• Simultaneously and independently
• Heizenberg realized that the reason Bohrs 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 h or DE.Dt h
• 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

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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
• n1, 2 and 3 for K, L and M shells respectively
• Corresponds to Bohrs 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

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• 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

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• 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
A
X
Z
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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-

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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

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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