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#7141 |
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9
4Be + n → 2(4 2He) + 2n Last edited by KurtCobain; 10-26-2011 at 06:40 PM.. |
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#7142 |
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As a metal, beryllium is transparent to most wavelengths of X-rays and gamma rays, making it useful for the output windows of X-ray tubes and other such apparatus.
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#7143 |
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It is also a good source for the relatively-small numbers of free neutrons in the laboratory which are liberated when beryllium nuclei are struck by energetic alpha particles[3] producing the nuclear reaction
9 4Be + 4 2He → 12 6C + n , where 4 2He is an alpha particle and 12 6C is a carbon-12 nucleus.[4] [edit]Isotopes and nucleosynthesis Main articles: Isotopes of beryllium and beryllium-10 |
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#7144 |
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Plot showing variations in solar activity, including variation in 10Be concentration.
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#7145 |
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Note that the beryllium scale is inverted, so increases on this scale indicate lower 10Be levels
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#7146 |
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Beryllium contains only one stable isotope, 9Be, and therefore is a monoisotopic element.
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#7147 |
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Cosmogenic 10Be is produced in the atmosphere of the Earth by the cosmic ray spallation of oxygen and nitrogen.
Last edited by KurtCobain; 10-26-2011 at 06:40 PM.. |
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#7148 |
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Cosmogenic 10Be accumulates at the soil surface, where its relatively long half-life (1.36 million years) permits a long residence time before decaying to boron-10.
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#7149 |
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Thus, 10Be and its daughter products are used to examine natural soil erosion, soil formation and the development of lateritic soils, and as a proxy for measurement of the variations in solar activity and the age of ice cores.[5]
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#7150 |
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The production of 10Be is inversely proportional to the solar activity,
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#7151 |
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because the increased solar wind during periods of high solar magnetic activity in turn decreases the flux of galactic cosmic rays that reach the Earth.
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#7152 |
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Nuclear explosions also form 10Be by the reaction of fast neutrons with 13C in the carbon dioxide in air.
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#7153 |
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This is one of the indicators of past activity at nuclear weapon test sites.[6]
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#7154 |
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The isotope 7Be (half-life 53 days) is also cosmogenic, and shows an atmospheric abundance linked to sunspots much like 10Be.
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#7155 |
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8Be has a very short half-life of about 7×10−17 s that contributes to its significant cosmological role, as elements heavier than beryllium could not have been produced by nuclear fusion in the Big Bang.[7]
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