Microscopic Versus Macroscopic Cross Section
Up to now, the cross section referred to in this article corresponds to the microscopic cross section σ. However, it is possible to define the macroscopic cross section Σ which corresponds to the total “equivalent area” of all target particles per unit volume:
where N is the atomic density of target.
Therefore, since the cross section can be expressed in cm2 and the density in cm−3, the macroscopic cross section is usually expressed in cm−1. Using equation derived in #Link to reaction rate and interpretation, the reaction rate per unit volume R can be derived using only the neutron flux Φ and the macroscopic cross section Σ:
Read more about this topic: Neutron Cross Section
Famous quotes containing the words microscopic, cross and/or section:
“The television screen, so unlike the movie screen, sharply reduced human beings, revealed them as small, trivial, flat, in two banal dimensions, drained of color. Wasn’t there something reassuring about it!—that human beings were in fact merely images of a kind registered in one another’s eyes and brains, phenomena composed of microscopic flickering dots like atoms. They were atoms—nothing more. A quick switch of the dial and they disappeared and who could lament the loss?”
—Joyce Carol Oates (b. 1938)
“The cross of the Legion of Honor has been conferred on me. However, few escape that distinction.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“Ah, Governor [Murphy, of New Jersey], don’t try to deceive me as to the sentiment of the dear people. I have been hearing from the West and the East, and the South seems to be the only section which approves of me at all, and that comes from merely a generous impulse, for even that section would deny me its votes.”
—William Howard Taft (1857–1930)