Radioactive /3-emitter. electron capture

Figure 29.5, depicts the diagram of an electron capture detector. The metal block of the detector housing itself serves as a cathode, whereas an electrode polarizing lead suitably positioned in the centre of the detector housing caters for a collector electrode (anode). The radioactive source from a beta-emitter is introduced from either sides of the detector housing below the electrode polarizing lead. 

Neutron activation of the stable isotopes of iron produces two radioactive isotopes—55Fe and 59Fe. 55Fe (half-life = 2.685 years), which is a beta (electron-capture) emitter and decays to the stable 55Mn isotope, is the more important isotope.10... 

Te 5.10 alpha particles and 5 beta particles 7. Refer to Table 21.2 for potential radioactive decay processes. 17F and, 8F contain too many protons or too few neutrons. Electron capture or positron production are both possible decay mechanisms that increase the neu-tron-to-proton ratio. Alpha-particle production also increases the neu-tron-to-proton ratio, but it is not likely for these light nuclei. 21F contains too many neutrons or too few protons. Beta-particle production lowers the neutron-to-proton ratio, so we expect 21F to be a /3-emitter. 9. a. 2gCf + gO - fcIJSg + 4jn b. Rf 11. 6.35 X 1011 13. a. 

Isotopic. Iron-55 is an electron-capture isotope with a half-life of 2.94 years. Iron-59 is a mixed /3-7 emitter the main radiations of which areO.27 M.e.v. 8 (46%), 0.46M.e.v. /8 (54%), 1.10 M.e.v. 7 (57%), and 1.29 M.e.v. 7 (43%). The half-life of Fe is 45.1 days. The radioactive samples are most readily assayed with a standard thin-mica-window Geiger counter which will detect mainly the Fe /3-particles. Decomposition of ferrocene and ferricinium salts in a boiling mixture of four parts by volume of concentrated nitric acid and one part of 75% perchloric acid and the subsequent electrodeposition of iron on copper disks gives samples which exhibit excellent counting reproducibility. 

Fig. 2.1 Nuclear resonance absorption of y-rays (Mossbauer effect) for nuclei with Z protons and N neutrons. The top left part shows the population of the excited state of the emitter by the radioactive decay of a mother isotope (Z, N ) via a- or P-emission, or K-capture (depending on the isotope). The right part shows the de-excitation of the absorber by re-emission of a y-photon or by radiationless emission of a conversion electron (thin arrows labeled y and e , respectively)...

The beta-current neutron detector is a solid state ion chamber which is used in nuclear reactor technology. It consists of an emitter in which a nuclear reaction occurs, leading to the emission of primary /3 particles (e.g. through the reaction ( Rh(n,7) Rh(/8 , 4.2 s) Pd) or secondary electrons (e.g. through absorption of the prompt y s emitted in the neutron capture). These electrons represent a current and are collected by a collector. The radioactive decay type detectors have a response time depending on the product half-life, which the capture-y detectors lack. These detectors have a limited lifetime for the Co(n,y) Co it amounts to 0.1 % per month at 10 n cm s . The lifetime depends on... 

Nuclear applications of nanocapsules are related to the emitting physical properties of the encapsulated material. Emitted radiation can be electromagnetic of high energy (y), electrons or positrons (/3), alpha particles (" He nucleus), or fission products [67]. These emitters can be in themselves radioactive or can be activated by a nuclear reaction, usually a neutron capture. The particular advantage of carbon nanocapsules in nuclear applications is related to the protective characteristics that the carbon capsule confers to the interior product. Experiments on irradiation of fullerenes have shown that knocked carbon atoms from one cage are foimd in another fuUerene and even form dimers and trimers by a recoil-implantation mechanism [68]. The observed major damage of capsules in nanoencapsulated molybdenum irradiated in a nuclear reactor was produced by... 

Radionuclides can be roughly divided into a-emitters and P-emitters. The emission of a-particles is associated with a decrease in mass number by four units and in the atomic number by two units. The loss oftwo protons results in an excess oftwo electrons, so the a-decay is accompanied by the emission of electrons (radiation P). In the radioactive P-type conversion, the nucleon in the atom nucleus transforms, a neutron turns into a proton or vice versa, which is associated with the change of particle charge and emitting an electron or positron. The capture of an electron (usually from the sphere K of the electron cloud) by the atom nucleus is also possible, while changing a proton into a neutron. In the electron cloud, the electron from the higher level then jumps to hll the vacant place, which is accompanied by the emission of a photon. ... 

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