Lecture_37

Lecture_37 - PHYS 342 Fall 2011 Lecture 37 Nuclear...

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PHYS 342 Fall 2011 Lecture 37: Nuclear Structure Ron Reifenberger irck Nanotechnology Center Birck Nanotechnology Center Purdue University Lecture 37 1
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Periodic Table – Mendeleev 1869 Elements organized by y atomic number: atomic number by atomic number: Organized by atomic number & chemical ctivity: activity 2 How do we learn about the internal nuclear structure of an atom?
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Atomic Size cattering Experiments: The Basic Idea Scattering Experiments: The Basic Idea What’s inside he box? B the box? A Two Limiting Scenarios: Result A: Box is filled with soft, fluffy material Result B: Box is filled with hard, rigid material 3
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Evidence for a Massive Nucleus: Rutherford’s Scattering Experiments 911) (1911) KEY QUESTION: We know gold foil is made of gold atoms that are electrically neutral. But how are the + and - charges distributed? (+) Typical Rutherford Scattering 172,000 events) A few of the particles are ackscattered! (, ) 1,000 2,000 3,000 4,000 mber of Event s x10 backscattered! onservation of energy and momentum imply the presence of 0 04 5 9 0 1 3 5 1 8 0 Scattering angle Nu m Conservation of energy and momentum imply the presence of small “heavy objects”. Rutherford concludes that the “heavy objects” are roughly ~10,000 times smaller than an atom!! 4
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What we now know: composition and approximate dimensions Atom (diameter 0.2 nm) Nucleus (diameter 3 fm) electrons proton neutron 1 fm = 1×10 -15 m neutron proton electron symbol harge e - P n 0 (zero) +1.602 x 10 -19 C- 1 .602 x 10 -19 C 5 charge mass () . . 1.675 x 10 -27 kg 1.673 x 10 -27 kg 9.109 x 10 -31 kg spin 1/2 1/2 1/2
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Nucleons - the basic building blocks of the nucleus Also written as: 7 3 Li xamples: A Z X ~10 -15 m Examples: X=Chemical Element A = atomic mass number = Z+N Z = number of protons = atomic number 12 6 C N= A-Z = number of neutrons 35 17 Cl 6
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This note was uploaded on 12/08/2011 for the course PHYS 342 taught by Professor Staff during the Fall '08 term at Purdue.

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Lecture_37 - PHYS 342 Fall 2011 Lecture 37 Nuclear...

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