Luminescence vs. Incandescence | VanCleave's Science Fun
Luminescence dating: basics, methods and applications comparing the natural luminescence signal of a sample with that induced .. due to black body radiation or incandescence. . In contrast to visible light, low-energy photons from the. Bioluminescence is the production of light by a living organism. 10 brief facts on bioluminescence. (, February 5). Retrieved May 20, Luminescence is “COLD LIGHT.”Cold light is light that usually occurs at low temperatures. Luminescence can be produced in many different.
In this case, it is called bioluminescence . Another kind is triboluminescence. This can be observed when a self-adhesive envelope is opened in complete darkness or when adhesive tape is unrolled in a dark room.
In doing so, mechanical energy is put into the system and serves as an activator for the glow . Probably the most familiar type of luminescence is photoluminescence. Here, energy is provided by electromagnetic radiation, for instance through sunlight or an ultraviolet lamp, as in some discotheques.
This causes phenomena like the ongoing glow of plastic stars or the extreme brightness of white clothes under black light. One can differentiate fluorescence and phosphorescence, which will be explained below .
What are Fluorescence and Phosphorescence? :: Education :: ChemistryViews
What is an Electronically Excited State? Generally, all kinds of luminescence are based on so-called photo-physical processes. Usually, molecules themselves are described as fluorescent.
This is the case with fluorescent dyes like fluorescein or curcumin [1,5]. However, to explain photo-physical processes, one has to take a closer look at an even smaller level than the molecular one.
Luminescence Dating: Applications in Earth Sciences and Archaeology
Atoms of different elements have a different number of electrons distributed into several shells and orbitals. Electrons are a type of elementary particle. Electronic transitions are responsible for luminescence [6,7]. When the system absorbs energy, electrons are excited and are lifted into a higher energetic state.
How this works exactly will be explained using photoluminescence as a specific example. Different energetic states of an atom or molecule are known as "energy levels".
Depending on the molecule and atom, the electrons can only occupy discrete energy levels since the energy is quantized, which means, energy can only be absorbed and emitted in certain amounts . The difference between two levels can be calculated with equation 1 where E2 is the higher energy level and E1 the lower one. Only light with a certain energy, and accordingly with a certain frequency and wavelength, is capable of exciting electrons . By equalizing equations 1 and 2, and with the help of equation 3 where c stands for the speed of lightthe necessary frequency and wavelength can be calculated see eq.
In many cases, UV-radiation is used for excitation. Electrons drop back to their ground states. At the same time, the excitation energy is released again.
One distinguishes between radiative and non-radiative decay processes. Most of the time, the decay is non-radiative, for example through vibrational relaxation, quenching with surrounding molecules, or internal conversion IC [6,7,10]. These processes will be explained in detail later. Sometimes, a radiative decay can occur in form of fluorescence and phosphorescence. The energy is emitted as electromagnetic radiation or photons. The emitted light has a longer wavelength and a lower energy than the absorbed light because a part of the energy has already been released in a non-radiative decay process .
This is the reason that an emission in the visible spectrum can be achieved by excitation with non-visible UV-radiation. This shift towards a longer wavelength is called Stokes shift . Phosphorescence Both fluorescence and phosphorescence are spontaneous emissions of electromagnetic radiation. The difference is that the glow of fluorescence stops right after the source of excitatory radiation is switched off, whereas for phosphorescence, an afterglow with durations of fractions of a second up to hours can occur [6,7].
Crystalloluminescence is a type of Luminescence generated during crystallization, used to determine the critical size of the crystal nucleus.
Separation of electrical charges may occur on the fracture facets on the surface of micro-fractures and their following recombination. This effectively classifies Crystalloluminescence as a type of Triboluminescence and a subtype of Electroluminescence.
Let us note that electrically charged micro-fractures may be developed due to multiple processes such as the movement of charged dislocations, piezoelectrification, etc.
Sonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound. It is believed that when a bubble starts imploding, extremely high pressures inside the bubble cause the water to form ice-like structures. At the moment when the opposite sides of an imploding bubble collide, the very strong mechanical stress causes the ice to fracture.
The growth of ice micro-fractures results in separation of electrical charges and their following recombination, which generates light. Therefore, Sonoluminescence is a part of Triboluminescence phenomenon. It is emitted at relatively short wavelengths, which can reach into the ultraviolet.
The emitting bubble size is averaged at about 1 mkm in diameter. The addition of a small amount of noble gas such as helium, argon, or xenon to the gas in the bubble enhances the intensity of the emitted light dramatically. Chemoluminescence is conversion of chemical energy directly into light as a result of a chemical reaction.
In brief, given reactants A and B are transformed into an excited intermediate I. The decay of the excited intermediate I to a lower energy level is responsible for the emission of light. The chemical substance luminol emits blue light upon contact with the iron in haemoglobin if blood is present. The glow lasts for about 30 seconds. Lightsticks is another well-known Chemoluminescence application.
Bioluminescence is Chemoluminescence produced by living organisms. 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 ]. Feldspar IRSL properties As mentioned above, wavelengths in the near infrared region peaking around nm can also be used to induce luminescence in feldspars. Since this effect was first noticed [ 72 ], most research in optical dating of feldspars has focused on IRSL stimulation.
The main advantage of using IRSL is that the rest of the visible spectrum can then be used for emission detection. Fine-grained sediments containing mixtures of both plagioclase and K-feldspars have also been demonstrated to display a major stimulation peak around nm as well as a weaker one at nm [ 73 ]. LEDs are much cheaper than lasers and are widely available, making them a desirable alternative.
With plagioclase feldspar, an IRSL emission peak has been identified at nm. Feldspars stimulated using IRSL following the administration of a laboratory dose also exhibit an emission peak at nm. That peak is not observed in feldspars that have a natural signal. When not required during dating, the peak can be removed by preheating the sample to an appropriate temperature.Luminescence generation
Calcite Thermally stimulated calcite has an emission maximum at nm [ 60 ]. However, efforts to use the mineral in luminescence dating have been encumbered by the limited environmental occurrence of calcite.
Luminescence vs. Incandescence
Calcite also tends to concentrate uranium in its lattice and this complicates dose rate calculations since isotopic disequilibrium of uranium has to be taken into account. Worth noting is that uranium disequilibrium dating can yield ages from calcite that are more reliable than those obtained using luminescence techniques.
As a result, the incentive to employ luminescence methods in dating calcite has been small. It should be mentioned that some of the earliest, albeit unsuccessful, TL studies that tried to date rocks employed calcite [ 10 ]. Other attempts to use calcite in archaeological dating include a report by Ugumori and Ikeya [ 76 ].
Zircon Zircon is an attractive dosimeter because it usually has a relatively high concentration of uranium. This yields a dose rate that is relatively constant since it is not susceptible to variations arising from external effects such as changes in water content or burial depth.
More Incandescence vs. Luminescece | VanCleave's Science Fun
An associated drawback, however, is that the uranium content of zircon varies between individual grains. Consequently, measurements for dose rate are made on single grains. Also notably, zircon crystal lattices often have natural inhomogeneities that make it difficult to make comparisons between artificial irradiation administered in the laboratory with natural doses originating from within the grain.
As outlined in Section 5, such comparisons are the standard approach for determining the paleodose when dating quartz or feldspar. To address that problem, zircon dating uses a technique called autoregeneration. With autoregeneration, after the natural signal from the zircon grains is measured, the grains are stored for a few months to allow a new dose to accrue. Measuring the signal at the end of the storage period and comparing it to the natural signal obtained from the initial measurement allows a calibration to be made that yields an age of the natural signal.
Analysis of zircon using TL includes a study by Huntley et al. OSL studies using zircon include investigations by Smith [ 78 ]. Paleodose and dose rate determination The age equation introduced in Section 1 Eq. This section examines methods that are used to determine the two variables.