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)
“I know we’re not saints or virgins or lunatics; we know all the lust and lavatory jokes, and most of the dirty people; we can catch buses and count our change and cross the roads and talk real sentences. But our innocence goes awfully deep, and our discreditable secret is that we don’t know anything at all, and our horrid inner secret is that we don’t care that we don’t.”
—Dylan Thomas (1914–1953)
“Socialite women meet socialite men and mate and breed socialite children so that we can fund small opera companies and ballet troupes because there is no government subsidy.”
—Sugar Rautbord, U.S. socialite fund-raiser and self-described “trash” novelist. As quoted in The Great Divide, book 2, section 7, by Studs Terkel (1988)