Alpha decay parent nucleus daughter nucleus Momentum conservation decides how the energy is distributed. r E 30 MeV 5 MeV.

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Presentation transcript:

alpha decay parent nucleus daughter nucleus Momentum conservation decides how the energy is distributed. r E 30 MeV 5 MeV

Decay Scheme of  -emission The nuclear reaction: 1600 y 3.82 d  94.6 % 5.4 %  Q  ns

beta decay kinetic energy number of  particles K max Energy spectrum and the conservation laws require another particle to be emitted or

Decay Scheme of  -emission The nuclear reaction: 110 min -- equivalent to: 0.8 % 99.2 % Q  ns

Decay Scheme of  -emission The nuclear reaction: 2.6 y ++ equivalent to: 0.05 % 90.0 % ps

gamma decay Very often the nucleus that undergoes radioactive decay is left in an excited state. In secondary decay the nucleus emits a high-energy photon. 4.4 MeV 13.4 MeV e-e- e-e-

electron capture Parent nucleus captures one of its shell electrons (K-electrons). A neutrino is difficult to detect. Electron capture is associated with x-ray emission caused by electronic transitions.

Decay Scheme for Electron Capture The nuclear reaction: EC equivalent to: 0.2 ns 2.78 d % 91 % e-e- Q  0.752

Positron-Electron Annihilation e-e- e+e+ h h Usually annihilation takes place at low kinetic energy of the particles. Conservation of momentum requires the emission of two (511 keV) photons emitted in the opposite directions. e + + e - = 2h

Pair Production h > 1.02 MeV e-e- e+e+ Almost the entire energy of the photon is used for the relativistic energy of the pair. The recoil of the nucleus satisfies the momentum conservation.

Photodisintegration The absorption of photons associated with photodisintegration occurs above precise energy thresholds causing removal of a nucleon from the nucleus 9 Be + h  8 Be + 1 n (1.66 MeV) 2 H + h  1 H + 1 n (2.22 MeV) Photodisintegration is used for calibration. 1n1n High energy photons (>20MeV) used to produce neutron beams..

Nuclear Fission Neutron bombardment of heavy nuclei may cause nuclear fission, in which a heavy nucleus is split into lighter nuclei. n n n

Fusion Reactions When two light nuclei combine to form a heavier nucleus, the process is called nuclear fusion. proton cycle: In the cycle four protons are combined to form an alpha particle and two positrons releasing 25 MeV of energy The reactions require high pressure and high temperature.