Editing Phosphorescence (section)

==Introduction==
[[File:JablonskiSimple.png|thumb|upright=1.25|[[Jablonski diagram]] of an energy scheme used to explain the difference between fluorescence and phosphorescence. The excitation of molecule A to its singlet excited state (<sup>1</sup>A*) may, after a short time between absorption and emission (fluorescence lifetime), return immediately to [[ground state]], giving off a photon via fluorescence (decay time). However, sustained excitation is followed by intersystem crossing to the triplet state (<sup>3</sup>A) that relaxes to the ground state by phosphorescence with much longer decay times.]]
In simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. This is in some cases the mechanism used for glow-in-the-dark materials which are "charged" by exposure to light. Unlike the relatively swift reactions in fluorescence, such as those seen in [[laser medium]]s like the common [[ruby]], phosphorescent materials "store" absorbed energy for a longer time, as the processes required to reemit energy occur less often. However, timescale is still only a general distinction, as there are slow-emitting fluorescent materials, for example [[uranyl salt]]s, and, likewise, some phosphorescent materials like [[zinc sulfide]] (in violet) are very fast. Scientifically, the phenomena are classified by the different mechanisms that produce the light, as materials that phosphoresce may be suitable for some purposes such as lighting, but may be completely unsuitable for others that require fluorescence, like lasers. Further blurring the lines, a substance may emit light by one, two, or all three mechanisms depending on the material and excitation conditions.{{explain|reason=What three mechanisms?|date=May 2024}}<ref>''New Trends in Fluorescence Spectroscopy'' by B Valeur -- Springer Page 5--6</ref>

When the stored energy becomes locked in by the spin of the atomic [[electron]]s, a [[triplet state]] can occur, slowing the emission of light, sometimes by several orders of magnitude. Because the atoms usually begin in a [[singlet state]] of spin, favoring fluorescence, these types of phosphors typically produce both types of emission during illumination, and then a dimmer afterglow of strictly phosphorescent light typically lasting less than a second after the illumination is switched off.

Conversely, when the stored energy is due to persistent phosphorescence, an entirely different process occurs without a fluorescence precursor. When electrons become trapped within a defect in the atomic or molecular lattice, light is prevented from reemitting until the electron can escape. To escape, the electron needs a boost of thermal energy to help spring it out of the trap and back into orbit around the atom. Only then can the atom emit a photon. Thus, persistent phosphorescence is highly dependent on the temperature of the material.<ref>''Persistent Phosphors: From Fundamentals to Applications'' by Jianrong Qiu, Yang Li, Yongchao Jia -- Elsevier 2020 Page 1--25</ref>