Ionising radiation alpha particles

Ionising radiation influences significantly the yield of c/oso-dodecaborate(2") labelling with l25I. Alpha radiation effect does show, probably due to rather localized character of interactions between alpha particles and solution, faster saturation compared to the effect of gamma radiation exhibiting more even distribution of radiolytical products (Figure 1). 

The main ionising radiations are alpha (a) particles, beta ((3) particles,... 

Alpha particles are so bulky that they do not usually travel more than 10 cm in air. They are easily stopped by card, brick or thin metal sheet. However, their mass and speed (typically about 10 ms ) means that they possess considerable kinetic energy and so cause substantial ionisation, and if brought into close contact with human tissue (for example, by ingestion) they usually cause much more damage than beta or gamma radiation. 

Ionising radiation. Radiation that produces ionisation in matter. Examples are alpha and beta particles, gamma and X-rays, and, indirectly, neutrons. 

Ionising radiation by alpha particles (= He Mons). In comparison with beta and gamma radiation, alpha radiation has the least penetrating power and the highest linear energy transfer. Radionuchde that decays to a more stable nuclide by emission of an alpha particle. 

When a radioactive nuclide decays, electrons are stripped from the parent atom by its recoil and decay products are formed as positive ions. These ions can attract liquid and even solid material, thus forming clusters of atoms or particles in the submicron region ranging from 0.001 to 0.01 pm. Air is permanently ionised by radiation from the natural radioactivity of air and by cosmic radiation which consists mostly of positively charged particles, 85% protons, 10% alpha particles with a smaller percentage of positively charged stripped nuclei of heavier elements, such as Fe, Co and Ni, etc. Production of an ion pair requires 35.6 eV if ionisation is by alpha particles and 32.5 eV if by fast electrons. In the free atmosphere, the rate of production of small ions is in balance with the rate of neutralisation by recombination and the rate of attachment to condensation nuclei. Condensation nuclei are mostly the Aitken nuclei, which are submicrometre particles in the range 0.005 to 0.01 pm. 

Alpha decay carries away positive charge and electrons are stripped from the parent atom by its recoil. Therefore, the decay products are formed as positive ions. Air is ionised by radiation from the naturally occurring radionuclides in the air and on the ground and by cosmic rays. Production of one ion pair requires 32.5 eV if ionisation is caused by fast electrons, 35.6 eV if by alpha particles. The total energy dissipated in air per decay of Rn depends on the equilibrium ratio of the radon decay products. 

As the name suggested this type of radiation consists of subatomic or groups of subatomic particles. Three sorts are recognised alpha, beta and neutrons. These and gamma radiation are termed ionising radiation. 

The a particle consists of two protons and two neutrons. It is therefore heavy and doubly charged. Alpha radiation has a very short range and is stopped by a few centimetres of air, a sheet of paper, or the outer dead layer of the skin. Outside the body, it does not, therefore, present a hazard. However, a-emitting radionuclides inside the body are of concern because a particles lose their energy to tissue in very short distances causing relatively intense local ionisation. 

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