Absorptionsquerschnitte

Absorptionsquerschnitte, often translated as absorption cross-sections, are a fundamental concept in physics, particularly in nuclear physics and particle physics, and also appear in areas like astrophysics and atmospheric science. They represent a measure of the probability that a particular particle will be absorbed by a target nucleus or atom. Conceptually, an absorption cross-section can be thought of as the effective area that a target presents to an incoming particle for the process of absorption.

The unit of absorption cross-section is typically area, commonly expressed in barns (1 barn = 10^-28 square meters). A larger absorption cross-section indicates a higher probability of absorption for a given flux of incident particles. The actual cross-section is not a physical size but rather a quantity that encapsulates the interaction probability.

Factors influencing the absorption cross-section include the type of incident particle, the type of target nucleus or atom, and the energy of the incident particle. For instance, neutron absorption cross-sections are highly dependent on neutron energy. Certain isotopes have very large absorption cross-sections for specific neutron energies, which is exploited in nuclear reactors for controlling the chain reaction. Similarly, the absorption of photons by matter is described by absorption cross-sections, which are crucial for understanding phenomena like spectroscopy and radiation shielding.