Types of Luminescence
Incandescence is light emitted from material because of the high temperature of the material. In a conventional incandescent light bulb, the excited atoms in the. Technically, delay time is the only difference between them. It is shorter for Fluorescence ( to s) and much longer for Phosphorescence (up to a few hours . carbon atoms, therefore eliminating the possibility of radiocarbon dating. But bulbs like this are incandescent and make light by making heat. What's the difference between luminescence, fluorescence, and.
Photoluminescence is distinguished in that the light is absorbed for a significant time, and generally produces light of a frequency that is lower than, but otherwise independent of, the frequency of the absorbed light. Chemiluminescence is luminescence where the energy is supplied by chemical reactions. Those glow-in-the-dark plastic tubes sold in amusement parks are examples of chemiluminescence. Bioluminescence is luminescence caused by chemical reactions in living things; it is a form of chemiluminescence.
Fireflies glow by bioluminescence. Electroluminescence is luminescence caused by electric current. Cathodoluminescence is electroluminescence caused by electron beams; this is how television pictures are formed on a CRT Cathode Ray Tube.
Other examples of electroluminescence are neon lights, the auroras, and lightning flashes. This should not be mistaken for what occurs with the ordinary incandescent electric lights, in which the electricity is used to produce heat, and it is the heat that in turn produces light.
More Incandescence vs. Luminescece | VanCleave's Science Fun
Radioluminescence is luminescence caused by nuclear radiation. Older glow-in-the-dark clock dials often used a paint with a radioactive material typically a radium compound and a radioluminescent material. The term may be used to refer to luminescence caused by X-rays, also called photoluminescence.
Phosphorescence is delayed luminescence or "afterglow". When an electron is kicked into a high-energy state, it may get trapped there for some time as if you lifted that rock, then set it on a table. In some cases, the electrons escape the trap in time; in other cases they remain trapped until some trigger gets them unstuck like the rock will remain on the table until something bumps it.
However, not all such minerals are suitable for use in luminescence dating. Today, luminescence dating primarily employs quartz and feldspar. Zircon and calcite have been tried in some studies but both minerals are associated with a number of complications. As a result, they are not commonly used in luminescence dating at present. This section examines the luminescence properties of the four minerals. In the discussions below, natural dose refers to energy acquired from natural radiation sources by a mineral grain in its field setting.
This is differentiated from an artificial dose that a sample would obtain when irradiated using an artificial source in a laboratory setting. Quartz Quartz is the most commonly used mineral in luminescence dating because it offers a number of advantages when contrasted with alternatives.
As a result, it is one of the most abundant minerals in clastic depositional environments. Additionally, it does not have an internal source of radiation as a major element of its composition. Thus, the ionizing radiation that quartz grains receive in nature is usually from an external source, which simplifies dose rate calculation procedures.
Situations exist, however, where quartz grains may contain very low levels of uranium but these are rare [ 51 ].
Luminescence and Fluorescence | FMS - The Fluorescent Mineral Society
For TL spectra, the sharp rise in emissions beyond nm is largely from incandescence rather than from electrons evicted from traps.
Quartz OSL properties Quartz has been shown to luminesce when stimulated by wavelengths from any part of the visible spectrum [ 60 ]. Most current OSL studies, however, prefer using blue light for stimulation because of the higher OSL intensities it yields [ 55 ].
Investigations have demonstrated that the OSL signal of quartz can consist of at least three or more components that are referred to as fast, medium and slow, based on their decay rates [ 6162 ].
Most regular dating procedures, however, employ a constant power continuous wave—CW and are unable to resolve the components. Through the use of heat treatments or stimulation for limited times to exclude the slower componentsdesired signals can be targeted when using CW stimulation. Main emission wavelengths for quartz and feldspars used in luminescence dating as well as wavelengths employed for stimulation.
Sensitivity ranges for some detectors are also shown. Feldspar Feldspar is another widely used mineral in OSL dating. In terms of chemistry, feldspars are aluminosilicates that form solid solution series with potassium K calcium Ca and sodium Na as end members of a ternary system.
Since potassium has an isotope that contributes ionizing radiation in luminescence dating, the potassium in K-feldspars has to be treated as a source of internal dose, in addition to dose contributions from sources external to the grains.
As a result, when dating feldspars, it is necessary to separate K-feldspars from Ca and Na-feldspars and analyze them separately. Compared with quartz, feldspar has a number of attractive luminescence features.
First, feldspar emissions are generally brighter than those from quartz which produces stronger signals.
- Luminescence Dating: Applications in Earth Sciences and Archaeology
- Types of Luminescence
This means that smaller doses can be measured during analysis. Second, the internal dose from potassium is not susceptible to external influences such as variations in pore water and this allows dose rates to be ascertained more accurately. Third, feldspar can be stimulated using infrared radiation which allows effective separation to be made between the stimulation source and emission wavelengths. The main drawback for feldspar, however, is its susceptibility to anomalous fading [ 64 ].
Anomalous fading occurs when trapped electrons reside in their traps for shorter periods than what would be predicted by physical models such that the luminescence intensity drops over time from the time of irradiation. Ultimately, the result of anomalous fading is that most feldspar grains yield equivalent doses that are slightly lower than they would in the absence of fading. Correction methods have been developed for dealing with anomalous fading when dating feldspars [ 6566 ].
In terms of emission wavelengths, K-rich feldspars have been reported [ 67 ] to show maximums in the range of — nm violet to blue. Conversely, emissions for some plagioclase feldspars have been reported to appear in the range of — nm blue-green. Other studies, however, have intimated at a more complex emission pattern for feldspars [ 68 ].
Feldspar OSL properties Optical stimulation of luminescence from feldspars has been investigated using visible light. Early studies employed lasers which included the The emissions were then monitored at shorter wavelengths [ 157 ] and shown to be centered around nm [ 69 ]. The application of OSL stimulation in dating feldspars, however, has been relatively limited because near-infrared stimulation discussed below has been shown to be a more desirable approach.
This would indicate that different trap types might be involved [ 50 ]. Apart from green and red stimulation, luminescence in feldspar has been demonstrated using a range of other wavelengths in the region spanning — nm [ 71 ]. Blue flashes of light will be generated! Triboluminescence happens quite a lot, it is just not seen at daylight conditions because it is typically weak. It happens when bonds in a material are broken because that material is scratched, crushed, or rubbed.
The effect is not really understood; separation and reunification of electrical charges seems to play a role; and there might simply be sparking in large electric fields.
Fractoluminescencepretty much the same thing as triboluminescence. Piezoluminescenceis produced by the action of pressure on, well, piezoelectric materials.
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It's different from the above because you do not need to break bonds but just some elastic deformation. Photoluminescence is caused by moving electrons to energetically higher levels through the absorption of photons. It's easily done in semiconductors with photons of energy larger than the bandgap, radiating recombination channels than produce bandgap light.
The solar cell picture above gives an example.