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Resonant photon absorption

This article explores resonant photon absorption and the Mossbauer effect, focusing on atomic interactions and the underlying mechanisms of photon attenuation. We delve into the properties of the source and absorber, examining how they affect resonant absorption in nuclear transitions, including kinematic effects and Doppler shifts. The discussion covers the significance of 57Fe isotopes, their nuclear states, and the implications of the nuclear Zeeman effect. Detailed analysis will also be given to the Pound-Rebka experiment, emphasizing its role in demonstrating Mossbauer resonant absorption. ###

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Resonant photon absorption

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  1. Resonant photon absorption The Mossbauer effect

  2. Source Detector x Absorber Atomic interactions Photon attenuation Radiation attenuation by:-- photoelectric effect-- compton scattering (E << 1.02 MeV)

  3. Source Detector x Absorber E* E* 0.0 0.0 Photon attenuation Consider nuclear resonant absorption Assumesourceandabsorberare identical

  4. emission absorption Source Detector x Absorber  for resonant absorption E* E* 0.0 0.0 Kinematics Assumesourceandabsorberare identical

  5. Ignore energy scale Source Absorber

  6. E* E* 0.0 0.0 Natural width of the state Estimates Consider an 57Fe source 57Co 57Co Fe

  7. Enter -- Mr. Mossbauer Place 57Fe source bound in a metal matrix Resonant Absorption! Place 57Fe absorber bound in a metal matrix

  8. +v -v Source Detector x Absorber E* E* 0.0 0.0 move source Kinematics Doppler shift frequency:h’- h = ED move source Assumesourceandabsorberare identical

  9. -v no resonant absorption Source Absorber

  10. -v no resonant absorption Source Absorber

  11. -v small resonant absorption Source Absorber

  12. -v more resonant absorption Source Absorber

  13. v = 0.0 maximum resonant absorption Source Absorber

  14. -v less resonant absorption Source Absorber

  15. -v small resonant absorption Source Absorber

  16. -v no resonant absorption Source Absorber

  17. -v no resonant absorption Source Absorber

  18. Resulting transmission curve

  19. Source Detector x Absorber Es* Ea* 0.0 0.0 Kinematics Assume source and absorber are NOT identical

  20. move absorber! +v -v Source Detector x Absorber Es* Ea* when - 0.0 0.0 Doppler kinematics Assume source and absorber are NOT identical Resonant absorption

  21. -v Absorber transition energy shifted no resonant absorption Source

  22. -v Absorber transition energy shifted small resonant absorption Source

  23. -v Absorber transition energy shifted more resonant absorption Source

  24. -v Absorber transition energy shifted more resonant absorption Source

  25. Absorber transition energy shifted v = 0.0 less resonant absorption Source

  26. -v Absorber transition energy shifted smallresonant absorption Source

  27. -v Absorber transition energy shifted no resonant absorption Source

  28. -v Absorber transition energy shifted no resonant absorption Source

  29. -v Absorber transition energy shifted no resonant absorption Source

  30. “Isotope shift” Doppler energy shifted

  31. move absorber! +v -v Source Detector x Absorber Es* Ea* 0.0 0.0 when - Isotope shift Isotope shift:Level shifts due to atomic electronic charge distribution in the nucleus. Resonant absorption Constant velocity data

  32. 57Fe What is the J for the ground state and the 14.4 Kev state? ENSDF/NNDS What is the multipolarity of the transition? What is the degeneracy for the-- ground state and the -- 14.4 Kev state? If there is a B field, then we can have a nuclear Zeeman effectthat will remove the degeneracies

  33. move source with constant acceleration -v +v Source Detector x Absorber m-sublevels Es* 0.0 57Fe

  34. Dipole transition selection rules

  35. = dwell time v = one channel 0 -v +v Source velocity curve t v = 0 maximum +v v = 0 time maximum -v v = 0 Source displacement curve Mossbauer resonant absorption with constant acceleration Use MCS/MCA data

  36. Source Detector x Absorber m-sublevels Es* 0.0 Possible absorption transitions

  37. m-sublevels Possible absorption transitions 6 4 2 5 3 1

  38. Possible absorption transitions Compare these predictions with the measurements… …follow guidelines in Problem. 10.C. and eventually determine

  39. The Pound-Rebecca Experiment Be prepared to explainwhat the experiment discoveredandhow the Mossbauer resonant photon absorption was essential to the measurement.

  40. m-sublevels Possible absorption transitions Case1 6 4 2 5 3 1

  41. m-sublevels Possible absorption transitions Case2 5 3 1 6 4 2

  42. 6 5 3 4 2 1 Possible absorption transitions m-sublevels Case3

  43. 6 5 4 3 2 1 Possible absorption transitions m-sublevels Case4

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