Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons (1n) participate in the following reaction:
1n + 14N → 14C + 1H
The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 50,000 ft) and at high geomagnetic latitudes, but the carbon-14 readily mixes and becomes evenly distributed throughout the atmosphere and reacts with oxygen to form radioactive carbon dioxide. Carbon dioxide also dissolves in water and thus permeates the oceans. Carbon-14 can also be produced in ice by fast neutrons causing spallation reactions in oxygen.
Carbon-14 then goes through radioactive beta decay.
\mathrm{~^{14}_{6}C}\rightarrow\mathrm{~^{14}_{7}N}+ e^- + \bar{\nu}_e
By emitting an electron and an electron antineutrino, carbon-14 (half life of 5730 years) decays into the stable (non-radioactive) isotope nitrogen-14.
The inventory of carbon-14 in Earth's biosphere is about 300 million Curies, of which most is in the oceans.[6]
gowns
chip resetter
Subject: Origin and radioactive decay 
Sun Dec 26, 2010 1:15 pm
