1. Importance of nuclear chemistry:
1. Atomic power stations and fuel production, reprocessing
2. Radiation technology in industry, agriculture and health-care (sterilization).
3. Medical applications:
a) radiopharmaceuticals, radio diagnosis;
b) radiotherapy.

2. Radiation sources: Radionuclides:
60Co radionuclid,  rays, energy 1.17 és 1.33 MeV, T1/2 5.3 years
137Cs radionuclid,  rays, energy 0.66 MeV, T1/2 30 years
90Sr-90Y radionuclids,  rays, max. energies and 2.25 MeV,
T1/2 28 years and 64 hours
Machine sources (monoenergetic, directed):
electron accelerators
heavy ion accelerators

3. Linear Energy Tansfer, LET:
It is the rate at which the particle loses energy, generally reported in units of eV/nm.
Radiation
LET, eV/nm
60Co- 1.17 and 1.33 MeV, 137Cs- 0.66 MeV,
90Sr- MeV, 90Y- 2.25 MeV
0.2 – 0.5
10 MeV accelerated electron
0.19
226Ra-, 4.8 MeV
145
1 MeV accelerated 4He2+ ion
190
10 MeV accelerated 4He2+ ion 92
10 MeV accelerated 16O8+ ion
1000

4. Radiation chemical yield (G(X)):
Quotient of n(X) by E
where: n(X) = mean amount of substance of a specified entity, X, produced, destroyed, or changed by the mean energy
imparted, E, to matter.
Unit: mol J–1. This quantity is often referred to as G-value.
The earlier unit was (100 eV)–1.
Exchange: 1 (100 eV)–1 = 1.0410–7 mol J–1.

5. n-Hexane H H H H H H │ │ │ │ │ │ 4.25 eV
H — C — C — C — C — C — C — H
│ │ │  │ │  │
H H H  H H  H
4.1 eV eV eV
Product
G, mol J–1 H2
0.5
C6H12
0.31
(C6H13)2
0.13
CH4
0.018
C2H4 + C2H6
0.067
C3H6 + n-C3H8
0.06
C4H8 + n-C4H10
0.05
C5H10 + n-C5H12
0.016

6. H
│  4.25 eV
H — C — H
│  eV
CH3 — C — H
│  eV
CH3 — C — H  4.0 eV │
2,3-Dimethylbutane
Product
G, mol J–1 H2
0.29
C6H12
Not measured
(C6H13)2
0.05
CH4
0.051
C2H4 + C2H6
0.01
C3H6 + n-C3H8
0.43
C4H8 + n-C4H10
0.015
C5H10 + n-C5H12
0.065

7. Conclusion:
Against the five orders of magnitude difference between the energy of the incident particle and that of the chemical bonds the product formation takes place with simple bond scissions. Generally there is only one bond scission in one molecule, multiple bond scissions are very rear. „Explosions” of the molecules to many smaller parts are not observed.
2. There is a well observable selectivity in the chemical bond decompositions. The scissions preferably take place at the weaker bonds.
3. There is a similarity in the product formation in radiolysis and photolysis. In photolysis the chemical decomposition usually takes place from the lowest energy excited states.

8. a) As a result of photon absorption the orbital symmetry changes.
Selection rules
a) As a result of photon absorption the orbital symmetry changes.
electric vector
s-orbit p-orbit
b) Electronic transition between states with the same multiplicities are allowed, between states with different multiplicities are forbidden.
c) The transition takes place with high probability if the vibrations in the ground state and in the excited state strongly overlap (Franck-Condon principle).

9. Energy deposition Radiation chemical approach
(How the molecule gains energy)
Collision of high energy electrons with molecules (hard collisions)
Interactions of 100 – eV electrons with molecules (soft collisions)
Interactions of 10 – 100 eV slow electrons with molecules
Scattering of electrons with  10 eV energy in the medium
Most of the excited and ionized molecules form in the interactions of 100 – eV fast electrons
Radiochemical approach
(How the particle looses energy)
-Rays
Photoeffect
Compton effect
Pair production
-Rays, accelerated electrons
Interaction with electron shell
Fast secondary electron
Characteristic X-ray
Interaction with nucleus
Continuous X-ray
During energy degradation large
number of fast electrons with
100 – eV energy are produced

10. Energy deposition
In the interactions of the very high-energy electrons large energy is transferred. For such interactions the model, which treats the system as a fast moving charged particle passing along the free electron at rest, gives a good description. In Coulomb interaction the free electron is set in motion at the expense of the energy of fast moving charged particle. The ‘probability’ dP for a charged particle with charge ze and speed u to transfer energy between Q and Q + dQ to an electron of the medium when passing unit distance is given by the equation below. me is the electron mass, NZ is the product of the number density of molecules, N, and the number of electrons in one molecule, Z, is the electron number density.

11. Energy deposition
For low values of Q, when Q is comparable to the binding energy of the electron, the soft collisions a model is applied which involves resonance-like absorption of energy. To the optical approximation theory the ‘probability’ of picking up energy between Q and Q + dQ is given by the equation shown below. df /dQ is the differential oscillation strength. df /dQ is proportional to the optical absorption coefficient. The logarithmic term varies slowly with Q, the probability of resonant transition is proportional to the ratio of optical absorption coefficient and transition energy. If the optical absorption spectrum is known, the transition probabilities and yields of excited molecules can be calculated.

12. Energy deposition
The fast moving charged particle passing by the molecule induces electric polarization in the molecule.
The characteristic time of polarization is in the order of 10–18 s, it is the timescale of photon absorption.
The effect exerted by a fast electron on the molecule is similar to the effect photon interaction.

13. Ionization, Excitation, Decomposition
Molecule, AB
Ionization, eV
ABAB++e-
Excitation, eV
ABAB*
Decomposition, eV
ABA+B
W-value, eV H2
15.4
11.3
4.5
36.5 N2
15.6
6.1
9.8
30.8 O2
12.1
0.9; 1.5; 4.2(T)
5.1
33.0 NO
9.3
5.3
6.5
H2O
12.6
7; 5(T)
29.6
CH4
12.7
8.5; 6.5(T)
27.3
c-C6H12
9.88 6
C-H 4.1; C-C 3.4
25.05
Benzene
9.25
4.7; 3.7(T)
C-H 4.7
20.9
Anthracene
7.5
3.2; 1.7(T)

14. Excitation spectrum, water vapor

15. Ionization
During gas phase ionization the ejected electron can easily escape the Coulomb field of the positve ion. The charges become homogeneously distributed in the medium: charge recombination occurs randomly (homogeneous recombination).
In condensed phases the fate of ion pairs and the nature of the recombination strongly depend on the properties of the medium.

16. e─ +
Apolar 
Polar

17. Ionization, recombination
In low-permittivity hydrocarbons, most of the ejected electrons lose the kinetic energy in interactions with the surrounding molecules and return to the gemanate ion (geminate recombination).
n-C6H14  n-C6H14+ + e− n-C6H14  n-C6H14* n-C6H14+ + e−  n-C6H14* n-C6H14*  n-C6H13 + H n-C6H14*  n-C6H12 + H2 H + n-C6H12  n-C6H11 + H2 2 n-C6H13  n-C6H12 + n-C6H  (C6H13)2

18. Ionization, recombination
In high-permittivity water most of the ejected electrons have sufficient energy to get away from the positive ion. After thermalization the electron orients the surrounding water molecules and stabilizes in the form of hydrated electron.
H2O /\/ H2O+ + e− H2O /\/ H2O* H2O+ + H2O  H3O+ + OH e−  + nH2O  eaq− H2O*  OH + H

19. Energy transfer Linear mixing rule
G(P)A and G(P)B are the yields of P product
from A and B, and A and B are the electron
fractions of A and B.
In mixtures the energy not necessary causes decomposition of the molecule where it was deposited. Inside liquid energy and charage transfer may take place. The H2 yield of benzene, 0.004 mol J−1, is 100 times smaller than G(H2) of n-hexane.
n-C6H14*+C6H6  n-C6H14+C6H6*
n-C6H14+ + C6H6  n-C6H14 + C6H6+

20. Energy transfer
In polystyrene radiolysis there is an enormous intramolecular protecting effect: due to the aromatic groups attached to the -C-C-C- backbone, the yield of disintegration is only 1% of that of polyethylene which does not contain aromatic substituents.
Polyethylene Polystyrene