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## Interaction of Electromagnetic Radiation with Matter

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**1. **Interaction of Electromagnetic Radiation with Matter N E 162 Lecture 5
Chapter 8 of Text book
Jasmina Vujic

**2. **Electromagnetic Radiation Its Nature and Properties: Dual Nature
Wave properties: ???m??????1/s???c (m/s) = ??
Particle Properties: m = 0, E = h?, p = E/c = h?/c = h/?
h?= 6.63 x 10-34 J s
Photons = Neutral
cannot steadily lose E as they penetrate matter
can travel some distance d before interacting with any atom
Photon can be absorbed - and it disappears,
Photon can scatter, changing its direction w/ or w/o E-loss

**3. **Electromagnetic spectrum

**4. **Interaction of Photons with Matter Photoelectric Effect
Compton Scattering
Pair Production
Photonuclear Reactions
In addition, there are two processes with very small energy transfer:
Thomson (elastic) scattering on a free electron, redirection of low energy photon without change in energy
Raleigh (coherent) scattering results from combined (coherent) action of an atom as a whole.

**5. **Photoelectric Effect Photoelectron is detected whenever a metal is illuminated by light of a frequency ??which is greater than a critical threshold frequency, irrespective of the intensity of light.
This is in direct conflict with prediction based on the wave nature of light (if light is classical wave: the electron should absorb E continuously and at any intensity, it should be just a matter of time until electron has sufficient E to escape. Thus there should be no threshold frequency).
Photoelectric effect could be explained if one assumed that the E carried by the incoming light came in discrete amounts. This amount only depends of ? and not on the intensity I
=Einstein in 1905 ->Nobel Prize in 1921

**6. **Photoelectric Effect

**7. **Compton Scattering

**8. **Compton Scattering
? = 00, h?max = h?, Tmin = 0
T= 1800, h?min = h?????? h??mc2)
Tmax = h????h?=2?h?????mc2/h??

**9. **The Klein-Nishina Formula for differential scattering cross section Per electron and per atom

**10. **The Klein-Nishina Formula coefficients Differential Klein-Nishina energy-transfer cross section:
Differential Klein-Nishina energy-scattering cross section:
The total Compton attenuation coefficient:

**11. **Pair Production

**12. **Photonuclear Reactions (?,n),(?,p), (?,2n), (?,?), (?,f) etc.
These are the threshold reactions - photon must have enough energy to overcome the binding energy of the ejected nucleon.
Need at least several MeV of photon energy.
206Pb(?,n)205Pb, Emin = 8 MeV

**13. **Total linear attenuation coefficient
Total mass attenuation coefficient

**14. **Total mass energy transfer coefficient
g takes into account the Bremsstrahlung contribution by the electrons freed in each process

**16. **Photon attenuation

**17. **Photon with Attenuation

**18. **Photon fluence for monoenergetic beam

**19. **Half-Value layer

**20. **Point Source

**21. **Tables of X-Ray Mass Attenuation Coefficients http://physics.nist.gov/PhysRefData/XrayMassCoef/cover.html
Tables of X-Ray Mass Attenuation Coefficients and Mass Energy-Absorption Coefficients from 1 keV to 20 MeV for Elements Z = 1 to 92and 48 Additional Substances of Dosimetric Interest*
J. H. Hubbell+ and S. M. Seltzer Ionizing Radiation Division, Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899

**22. **Tables of X-Ray Mass Attenuation and Mass Energy Absorption Coefficients Abstract: Tables and graphs of the photon mass attenuation coefficient ??? and the mass energy-absorption coefficient ?en/? are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV. The ??? values are taken from the current photon interaction database at the National Institute of Standards and Technology, and the ?en/? values are based on the new calculations by Seltzer described in Radiation Research 136, 147 (1993). These tables of ??? and ?en/? replace and extend the tables given by Hubbell in the International Journal of Applied Radiation and Isotopes 33, 1269 (1982).

**23. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z08.html

**24. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z19.html

**25. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ElemTab/z82.html

**26. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/bone.html

**27. **Bone, Cortical (ICRU-44) - Composition Z/A = 0.51478 I (eV)=112.0 ?=1.920E+00 (g/cm3)
I - mean excitation energy
H-1: 0.034000
C-6: 0.155000
N-7: 0.042000
O-8: 0.435000
Na-11: 0.001000
Mg-12: 0.002000
P-15: 0.103000
S-16: 0.003000
Ca-20: 0.225000

**28. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/tissue.html

**29. **Tissue, Soft (ICRU Four-Component) Z/A = 0.54975 I(eV)=74.9 ? = 1.000E+00 (g/cm3)
1: 0.101174
6: 0.111000
7: 0.026000
8: 0.761826

**30. **http://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/water.html