what is a barn? all i know is that it is a unit of area
doing something with atoms. HELP!!!!!!!
The barn is a unit of capture cross section of an atomic nucleus. Cross
section is a measure of the probability of something interacting with a
nucleus, such as neutron capture. Cross section is expressed as a/(bc),
where a is the number of processes occurring, b is the number of particles
that could potentially interact with the nuclei, and c is the number of
target nuclei per square centimeter. So, this will be in units of square
centimeters. This can be expressed as an effective cross-sectional area
per nucleus. A barn is 10^(-24) square centimeters per nucleus. It was
given this name because it corresponds to a very large cross section;
hitting a nucleus with a cross section of 1 barn is as easy as hitting the
braod side of a barn.
Richard Barrans Jr., Ph.D.
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Update: June 2012