Underlying Physics
When materials are exposed to short-wavelength X-rays or to gamma rays, ionization of their component atoms may take place. Ionization consists of the ejection of one or more electrons from the atom, and may occur if the atom is exposed to radiation with an energy greater than its ionization potential. X-rays and gamma rays can be energetic enough to expel tightly held electrons from the inner orbitals of the atom. The removal of an electron in this way renders the electronic structure of the atom unstable, and electrons in higher orbitals "fall" into the lower orbital to fill the hole left behind. In falling, energy is released in the form of a photon, the energy of which is equal to the energy difference of the two orbitals involved. Thus, the material emits radiation, which has energy characteristic of the atoms present. The term fluorescence is applied to phenomena in which the absorption of radiation of a specific energy results in the re-emission of radiation of a different energy (generally lower).
Read more about this topic: X-ray Fluorescence
Famous quotes containing the words underlying and/or physics:
“The welfare, the happiness, the energy and spirit of the men and women who do the daily work ... is the underlying necessity of all prosperity.... There can be nothing wholesome unless their life is wholesome; there can be no contentment unless they are contented.”
—Woodrow Wilson (1856–1924)
“But this invites the occult mind,
Cancels our physics with a sneer,
And spatters all we knew of denouement
Across the expedient and wicked stones.”
—Karl Shapiro (b. 1913)