05-12-2023-1614 - phosphoroscope, tritium, phosphorescence, fluorophor, sensitizers, promethium, 61, ground state, dangling bond, molybdenum disulfide, electron microscope, lattice, singlet, triplet, dye lasers, cathodoluminescence, defect, ac current cycle, off time, blurring, mergence, etc. (draft)

Common examples include the phosphor coatings used in fluorescent lamps, where phosphorescence on the order of milliseconds or longer is useful for filling in the "off-time" between AC current cycles, helping to reduce "flicker". Phosphors with faster decay times are used in applications like the pixels excited by free electrons (cathodoluminescence) in cathode-ray tube television-sets, which are slow enough to allow the formation of a picture as the electron beam scans the screen, but fast enough to prevent the frames from blurring together.^[13][14] Even substances commonly associated with fluorescence may in fact be prone to phosphorescence, such as the liquid dyes found in highlighter pens, which is a common problem in liquid dye lasers. The onset of phosphorescence in this case can sometimes be reduced or delayed significantly by the use of triplet-quenching agents.^[15]

Equation

$${\displaystyle S_0+h\nu \to S_1\to T_1\to S_0+h{\nu }^{\mathrm{\prime }}}$$

where S is a singlet and T a triplet whose subscripts denote states (0 is the ground state, and 1 the excited state). Transitions can also occur to higher energy levels, but the first excited state is denoted for simplicity.

https://en.wikipedia.org/wiki/Phosphorescence

When a defect occurs, depending on the type and material, it can create a hole, or a "trap". For example, a missing oxygen atom from a zinc oxide compound creates a hole in the lattice,  

https://en.wikipedia.org/wiki/Phosphorescence

A vacancy defect, where an atom is simply missing from its place, leaving an empty "hole", is one type of defect. Sometimes atoms can move from place to place within the lattice, creating Schottky defects or Frenkel defects. Other defects can occur from impurities in the lattice.

https://en.wikipedia.org/wiki/Phosphorescence

For example, when a normal atom is substituted by a different atom of much larger or smaller size, a substitutional defect occurs, while an interstitial defect occurs when a much smaller atom gets trapped in the "interstices", or the spaces between atoms. In contrast, amorphous materials have no "long-range order" (beyond the space of a few atoms in any direction), thus by definition are filled with defects.  

https://en.wikipedia.org/wiki/Phosphorescence

An electron microscope reveals vacancy defects in a crystalline lattice of molybdenum disulfide. The missing sulfur atoms leave dangling bonds between the molybdenum atoms, creating a trap in the empty spaces.

https://en.wikipedia.org/wiki/Phosphorescence

When a defect occurs, depending on the type and material, it can create a hole, or a "trap". For example, a missing oxygen atom from a zinc oxide compound creates a hole in the lattice, surrounded by unbound zinc-atoms. This creates a net force or attraction that can be measured in electron-volts. When a high-energy photon strikes one of the zinc atoms, its electron absorbs the photon and is thrown out into a higher orbit. The electron may then enter the trap and be held in place (out of its normal orbit) by the attraction. To trigger the release of the energy, a random spike in thermal energy is needed of sufficient magnitude to boost the electron out of the trap and back into its normal orbit. Once in orbit, the electron's energy can drop back to normal (ground state) resulting in the release of a photon.^[16]

^{https://en.wikipedia.org/wiki/Phosphorescence}

The release of energy in this way is a completely random process, governed mostly by the average temperature of the material versus the "depth" of the trap, or how many electron-volts it exerts. A trap that has a depth of 2.0 electron-volts would require a great amount of thermal energy (very high temperatures) to overcome the attraction, while at a depth of 0.1 electron-volts very little heat (very cold temperatures) are needed for the trap to even hold an electron. Higher temperatures may cause the faster release of energy, resulting in a brighter yet short-lived emission, while lower temperatures may produce dimmer but longer-lasting glows. Temperatures that are too hot or cold, depending on the substance, may not allow the accumulation or release of energy at all. The ideal depth of trap for persistent phosphorescence at room temperature is typically between 0.6 and 0.7 electron-volts.^[17] If the phosphorescent quantum yield is high, that is, if the substance has a large number of traps of the correct depth, these substances will release significant amounts of light over long time scales, creating so-called "glow in the dark" materials.

Persistent phosphorescence is the mechanism of most anything commonly referred to as glow in the dark. Typical uses include toys, frisbees and balls, safety signs, paints and markings, make-ups, art and décor, and a variety of other uses. 

Chemiluminescence

Main article: Chemiluminescence

Some examples of glow-in-the-dark materials do not glow by phosphorescence. For example, glow sticks glow due to a chemiluminescent process which is commonly mistaken for phosphorescence. In chemiluminescence, an excited state is created via a chemical reaction. The light emission tracks the kinetic progress of the underlying chemical reaction. The excited state will then transfer to a dye molecule, also known as a sensitizer or fluorophor, and subsequently fluoresce back to the ground state.

 

https://en.wikipedia.org/wiki/Phosphorescence

https://en.wikipedia.org/wiki/Phosphorescence

https://en.wikipedia.org/wiki/Cathode-ray_tube

https://en.wikipedia.org/wiki/Promethium

https://en.wikipedia.org/wiki/Luminous_gemstones

https://en.wikipedia.org/wiki/Phosphoroscope

https://en.wikipedia.org/wiki/Tritium

https://en.wikipedia.org/wiki/Persistent_luminescence

https://en.wikipedia.org/wiki/Microparticle#Microspheres

https://en.wikipedia.org/wiki/Type_system#DYNAMIC

 ^{https://en.wikipedia.org/wiki/Downcasting}

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^{https://en.wikipedia.org/wiki/Tagged_union}

^{https://en.wikipedia.org/wiki/Dynamic_dispatch}

^{https://en.wikipedia.org/wiki/Disjoint_union}

^{https://en.wikipedia.org/wiki/Subtyping}

^{https://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science)}

^{https://en.wikipedia.org/wiki/Subtyping}

^{https://en.wikipedia.org/wiki/Reflective_programming}

^{https://en.wikipedia.org/wiki/Late_binding}

^{https://en.wikipedia.org/wiki/Dynamic_dispatch}

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^{https://en.wikipedia.org/wiki/Trade-off}

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^{https://en.wikipedia.org/wiki/Interpreter_(computing)}

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^{https://en.wikipedia.org/wiki/Duck_typing#Comparison_with_other_type_systems}

^{https://en.wikipedia.org/wiki/Generic_programming}

^{https://en.wikipedia.org/wiki/Strong_and_weak_typing}

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^{https://en.wikipedia.org/wiki/PurifyPlus}

^{https://en.wikipedia.org/wiki/Gradual_typing}

^{https://en.wikipedia.org/wiki/Type_system#STATIC}

^{https://en.wikipedia.org/wiki/Associative_array}

^{https://en.wikipedia.org/wiki/Modular_programming}

^{https://en.wikipedia.org/wiki/Abstraction_(computer_science)}

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^{https://en.wikipedia.org/wiki/SECD_machine#Landin's_contribution}

^{https://en.wikipedia.org/wiki/Lambda_calculus}

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^{https://en.wikipedia.org/wiki/Epigram_(programming_language)}

^{https://en.wikipedia.org/wiki/Infinite_loop}

^{https://en.wikipedia.org/wiki/Substructural_type_system#Linear_type_systems}

^{https://en.wikipedia.org/wiki/Immutable_object}

^{https://en.wikipedia.org/wiki/Referential_transparency}

^{https://en.wikipedia.org/wiki/Intersection_type}

^{https://en.wikipedia.org/wiki/Refinement_type}

^{https://en.wikipedia.org/wiki/Existential_quantification}

^{https://en.wikipedia.org/wiki/Record_(computer_science)}

^{https://en.wikipedia.org/wiki/System_F}

^{https://en.wikipedia.org/wiki/Compile_time}

^{https://en.wikipedia.org/wiki/Runtime_(program_lifecycle_phase)}

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^{https://en.wikipedia.org/wiki/Array_(data_structure)}

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^{https://en.wikipedia.org/wiki/Decision_problem}

^{https://en.wikipedia.org/wiki/Structural_type_system}

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^{https://en.wikipedia.org/wiki/Ad_hoc_polymorphism}

^{https://en.wikipedia.org/wiki/Type_signature}