Page 138 - Radiochemistry and nuclear chemistry

124
Ionization, (atomic) excitation
Nuclear (coulomb) excitation
Nuclear trammutation
Positron annihilation
Nuclear photo effect
scattering
Nuclear excitation
Nuclear scattering
M6ssbauer effect
Bremsstrahlung
Compton effect
Pair formation
photo effect
Coherent
0.01
10-3
i 1W)
(100%)
0.1
10
> I@
<I
>I
5
5
5
MeV)
= 20
magnitude at about 1 MeV in 2
1
y annihilated, formation of positrownegatron pair (E, > 1.02 MeV)
Particle captured, formation of comparnd nucleus (E, > E&in)@)
Particle scattered with energy loss. continucus emission of h v(E,
5 MeV)*)
Particle energy loss through atomic excitation and ionization
TABLE 6.1. Survey of nuclear radiation absorption pmesses
>
y completely absorbed, one electron knocked out
y absorbed by mleus, mlear transmutation (E,
annihilated, 2-3 phdons formed
y scattered with energy loss, ionization
Type of reaction U Name of process (barn) Ionization, (atomic) excitation lo' 2 through atomic excitation and ionization Radiochemistry and Nuclear Chemistry Neutron moderation 5 10 Neutroncapture i l(r
reaction cross-sections (0) give only order of
Particle energy loss Particle elastically scattered Particle inelastically scattered Slow p' y scattered witholll energy loss y scattered without energy loss y scattered with ene%y loss n scattered with energy loss n captured. nuclear transformation strongly with decreasing energy. 1.6 MeV, D(y,n)H 2.2 MeV.
The react with is the Coulomb barrier energy, eqn. (12.18).
Reacting particles and fields Protovts Md heavier ions react with orbital electrons 4 atomic nucleus Electrons (e-, p-, pi) orbital electrons electric feld of nucleus (y) react with field of orbital electrons (outer) electrons bound (irmer) electrons Rlclear force atomic nucleus Neutrons react with atomic nucleus See Fig. 6.17; u increases Threshold energy for Ek(y,a)'He
Photons
field of
free
(') @) &(min) (')
1 la Id 2 2b 2c 3 3a 3b 3c 3d 4 4b