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Scattering by an atom

Scattering by an atom. Atomic Scattering Factor. dE a. S - S o. S. dV. 2 q. r. S o. charge in dV:. Scattering by dV:. spherical cloud of electrons (assumed). Notes: 11/2/99 pg. 1 pg. 2. Notes: 10/28/99 pg. 1 pg. 2. Scattering by an atom. Atomic Scattering Factor.

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Scattering by an atom

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  1. Scattering by an atom Atomic Scattering Factor dEa S-So S dV 2q r So charge in dV: Scattering by dV: spherical cloud of electrons (assumed) Notes: 11/2/99 pg. 1 pg. 2 Notes: 10/28/99 pg. 1 pg. 2

  2. Scattering by an atom Atomic Scattering Factor

  3. Atomic scattering factor • 6 ions and one neutral atom - each with 10 electrons • As nuclear charge increases, electrons are drawn closer to the nucleus, pathlength differences are decreased, and scattering curves deviate less and less from the “point” atom (zero path differences) • The outermost (weakly bound) electrons make appreciable contributions to the total scattering only at small angles • Innermost electrons (K shell) contribute to scattering at all angles, contributions from L shell electrons falls off more rapidly, and valence electrons make small total contributions limited to small angles Notes 11/4/99 pg. 1 pg. 2 pg. 3 pg. 4 pg. 5

  4. Atomic scattering factor Lithium (Z = 3) Hydrogen (Z = 1)

  5. Scattering Summarized

  6. Structure Factor Let B be located at x y z or fractional coordinates

  7. Structure Factor Vector summation of E1 and E2

  8. Structure Factor Notes: 11/11/99 pg. 1 pg. 2 pg. 3 Notes: 11/9/99 pg. 1 pg. 2

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