2. Resonant photon absorption The Mossbauer effect

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

4. Photon attenuation Consider nuclear resonant absorption SourceDetector Absorber xx 0.0 E*E* E*E* Assume source and absorber are identical

5. Kinematics Assume source and absorber are identical SourceDetector Absorber xx 0.0 E*E* E*E* emissionabsorption  for resonant absorption

6. SourceAbsorber Ignore energy scale

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

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

9. Kinematics Assume source and absorber are identical -v+v SourceDetector Absorber xx 0.0 E*E* E*E* move source Doppler shift  frequency: h ’- h = E D

10. SourceAbsorber -v no resonant absorption

11. SourceAbsorber -v no resonant absorption

12. SourceAbsorber -v small resonant absorption

13. SourceAbsorber -v more resonant absorption

14. SourceAbsorber v = 0.0 maximum resonant absorption

15. SourceAbsorber -v less resonant absorption

16. SourceAbsorber -v small resonant absorption

17. SourceAbsorber -v no resonant absorption

18. SourceAbsorber -v no resonant absorption

19. Resulting transmission curve

20. Kinematics Assume source and absorber are NOT identical SourceDetector Absorber xx 0.0 Ea*Ea* Es*Es*

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

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

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

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

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

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

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

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

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

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

31. Doppler energy shifted “Isotope shift”

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

33. 57 Fe 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 effect that will remove the degeneracies

34. 57 Fe +v-v move source with constant acceleration SourceDetector Absorber xx 0.0 Es*Es* m-sublevels

35. Dipole transition selection rules

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

37. Possible absorption transitions SourceDetector Absorber xx 0.0 Es*Es* m-sublevels

38. Possible absorption transitions m-sublevels 654321

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

40. The Pound-Rebecca Experiment Be prepared to explain what the experiment discovered and how the Mossbauer resonant photon absorption was essential to the measurement.

41. Possible absorption transitions m-sublevels 654321 Case 1

42. Possible absorption transitions m-sublevels 563412 Case 2

43. Possible absorption transitions m-sublevels 652314 Case 3

44. Possible absorption transitions m-sublevels 652413 Case 4