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Heavy ions, γ -photons, fast electrons – all of them produce

. Heavy ions, γ -photons, fast electrons – all of them produce low-energy secondary electrons in the medium ( γ : photoeffect, Compton-effect, pair production). The good part of the electron energy is imparted to the atoms/molecules of the medium via Coulomb interaction.

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Heavy ions, γ -photons, fast electrons – all of them produce

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  1. .

  2. Heavy ions, γ-photons, fast electrons – all of them produce low-energy secondary electrons in the medium (γ: photoeffect, Compton-effect, pair production). The good part of the electron energy is imparted to the atoms/molecules of the medium via Coulomb interaction

  3. Optical approximation– as if the medium were illuminated with white light. Hence: energy absorption is connected with optical absorption spectra.

  4. Types, sources of radiation α210Po (E=5,3 MeV) β90Sr (Emax=2,18 MeV, <E>=0,765 MeV) Accelerators: van de Graaff, LINAC, etc. γ60Co (E=1,1; 1,3 MeV, <E>=1,25 MeV)

  5. Energy loss of a charged fast particle: Bragg-curve: Number of ions as a function of depth

  6. Bragg-Gray : γ dose, measured in a thimble chamber Ideal case – poliethylene thimble filled with ethylene gas

  7. Absolute dosimetry: Dose D coming from a volume element of the source, reaching a volume element of the irradiated space One must know the activity of the source, then must be integrated over source and irradiated space. r

  8. Radolysis of water This was written in 1907. Ramsay thought it was a question of total energy. Others compared water radiolysis with electrolysis

  9. Does this type of reaction scheme explain more than it was devised to? Effect of LET on the yields of radiaton chemical processes .

  10. Diffusion controlled kinetics Heavy ion Fast electron trajectories observed in a cloud chamber Radiolysis products are not distributed homogeneously – hence diffusion, recombination and chemical reaction proceed simultaneously and in interaction.

  11. Radical diffusion theory Neutral radicals, hence no Coulomb interaction. Number of equations = number of radical types. Coupled equations LET effect due to different initial geometries.

  12. Highland Park, USA, 1951

  13. Some suspicion: two types of „H-atoms”?

  14. Pulse radiolysis (a sister of flash photolysis) Accelerators, with short and shorter pulse lengths are needed. A not-too-modern equipment: Pune (India) 2006

  15. The first spectrun of the hydrated electron (Hart and Boag, 1962) As it was expected.

  16. The first kinetic trace of the hydrated electron (Keene, 1963)

  17. Chemistry of the hydrated electron - The ideal of the reducing agent: no oxidised product left - the perfect nucleophyilic partner - very selective, in certain cases diffusion controlled rates - previously unknown products, e.g.Ag0, Cu0 A naive model (polaron in a dielectric medium)

  18. Hydrated Electrons in Water Clusters: Inside or Outside, Cavity or Noncavity? László Turi* Department of Physical Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest 112, H-1518 Hungary J. Chem. Theory Comput., 2015, 11 (4), pp 1745–1755

  19. Detour – in parenthesis (Simultaneous diffusion and migration: Markov-process Master equation Fokker-Planck equation: c = concentration ; P = probability. But, as we know…)

  20. Is electron formation a particular wonder? Onsager problem: simultaneous ion migration and diffusion – with the result: recombination. Steady state approximation R + Ibe e Iki e If so, complete ion-electron recombination would proceed.

  21. Solvated electrons discovered in a good number of polar liquids: alcohols, amines, ethers Electron spectra:

  22. Electron yields in a series of polar liquids: the effect of energy fluctuations

  23. Hydrated electron yield in supercooled water

  24. Excess electrons in a number of non-polar liquids Electron mobilities Hel, Xel, n-hexane, neo-pentane χ[10-3, 103] cm2/Vs Energy of the localized state: Et ; Bottom of the conductivity band: V0 Et < V0  lokalizáció (buborék) Localization probability, P, defined by energy fluctuation:

  25. Radiaton chemistry of organic molecules R-CH2-CH2-R’ R-CH2··CH2-R’ R-CH2· + R-CH2-CH2-R’RCH3 + R-C·H-CH2-R’ H· + R-CH2-CH2-R’ H2+ R-C·H-CH2-R’ Generally speaking: bond cleavage and bond formation. Main product usually H2 The failure of the organic moderated reactors. But: chemistry of the nuclear reactors!!

  26. β irradiation of oxidized iron surfaces, after that electrode Impedance in aquoeus SO32- solution (hole capture). Equivalent circuit: Result: Faraday process gets faster due to irradiation

  27. γ irradiation of carbon steels (Daub (2011) Irradiation in aqueous solutions at different pH values Ecorr= -0.65 V Ecorr= 0 V SCE; pH 10,6 γ-Fe2O3 is formed upon the irradiated surface. Raman spectra  for comparison

  28. Hydrogen economy Hydrogen from water. Catalytic cycle: 2AB + 2H2O  2AH + 2BOH 2BOH  2B + ½O2 + H2O 2AH  2A + H2 2A + 2B  2AB Low-temperature extotherm, and high-temperature endotherm stages are desired. High temperature is always needed! Gas-cooled nuclear reactors?

  29. For example: UT-3 Process CaBr2 + H2O  CaO + 2HBr [700 0C] CaO + Br2 CaBr2 + ½O2[550 0C] Fe3O4 + 8HBr  3FeBr2 + 4H2O + Br2[250 0C] 3FeBr2 + 4H2O  Fe3O4 + 6HBr + H2[600 0C]

  30. Another possibility:

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