Radiation from beryllium

With respect to coal emissions, mercury, for example, was found to exist principally (as much as 96% ) in the elemental form (30). Previously, it was argued by some that ultraviolet radiation transformed it to the less toxic mercuric oxide (30). Sunlight tends to degrade mercurial compounds to the elemental form (47). Beryllium emissions from coal combustion may be in the nontoxic elemental form (46), but this is not known for certain. Fluoride, which is generally assumed to be 100% volatized (19), may be trapped with lime in particulates (33), but this also is questionable. Highly toxic nickel carbonyl (48) and arsine (49) emissions have not been reported to date, although the former is a distinct possibility (50). 

The Joliot-Curies decided next to see if the beryllium radiation would knock protons out of matter as alpha particles did. They fitted their ionization chamber with a thin window, explains Feather, and placed various materials close to the window in the path of the radiation. They found nothing, except with materials such as paraffin wax and cellophane which already contained hydrogen in chemical combination. When thin layers of these substances were close to the window, the current in the ionization chamber was greater than usual. By a series of experimental tests, both simple and elegant, they produced convincing evidence that this excess ionization was due to protons ejected from the hydrogenous material. The Joliot-Curies understood then that what they were seeing were elastic collisions—like the collisions of billiard balls or marbles—between the beryllium radiation and the nuclei of H atoms. 

But they were still committed to their previous conviction that the penetrating radiation from beryllium was gamma radiation. They had not... 

As a consequence, one was searching for a neutral particle. More by chance, Bothe and Becker (Bothe and Becker 1930a, b) found an unusnally hard (energetic) y radiation emitted when light elements like lithium and beryllium were exposed to a radiation. From the absorption in lead, they calculated an energy of 10 MeV. This radiation was also studied by Curie and Joliot (Curie and Joliot 1932). These authors found that protons were ejected from paraffin and calculated a y -ray energy of even 50 MeV - a large discrepancy fi-om the results of Bothe and Becker. 

The neutron was discovered in 1932 by the English physicist James Chadwick (1891-1974). It had been observed in 1930 by two German investigators, Bothe and Becker, that a very penetrating radiation is produced when beryllium metal is bombarded with alpha particles from radium. Bothe and Becker considered the radiation to consist of y-rays. Frederic Joliot and his wife Irene Joliot-Curie then discovered that this radiation from beryllium, when passed through a block of paraffin or... 

In 1930 two scientists, W. Bothe and H. Becker, observed that when a-particles in the radiation from the radioactive elements polonium or radium penetrated beryllium a previously unknown radiation was produced. The charge of the particles in this new radiation was examined in a cloud chamber, but no tracks were formed. Thus, the new particles had no charge. James Chadwick in 1932 solved the problem by proposing a particle having a mass about the same as the proton but without a charge. This particle he called the neutron. The reaction that produced the neutron was ... 

When beryllium is bombarded with alpha particles, a penetrating radiation is given off that is not deflected by electric or magnetic fields. Therefore, the radiation does not consist of charged particles. The British physicist James Chadwick (1891—1974) suggested in 1932 that the radiation from beryllium consists of neutral particles, each with a mass approximately that of a proton. The particles are called neutrons. The reaction that resulted in the discovery of the neutron is... 

Neutron radiation is emitted in fission and generally not spontaneously, although a few heavy radionueleides, e.g. plutonium, undergo spontaneous fission. More often it results from bombarding beryllium atoms with an a-emitter. Neutron radiation deeays into protons and eleetrons with a half-life of about 12 min and is extremely penetrating. 

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