Calorescence
Encyclopedia
Calorescence is a word for when matter absorbs infrared
radiant energy and emits visible radiant energy in its place. For example, some kinds of flammable gas give off large amounts of radiant heat and very little visible light when burning, and if a piece of metal is placed into such a flame, the metal will become bright red-hot—which is to say the metal absorbs invisible infrared and emits visible radiation. The word calorescence was coined in 1864 on the model of the word fluorescence
which had been coined in 1852. At that time, fluorescence was defined as absorption in the ultraviolet part of the spectrum followed by emission in the visible part of the spectrum. Calorescence was defined complementarily as absorption in the infrared followed by emission in the visible.
The following is a laboratory demonstration of calorescence. An ordinary lightbulb emits lots of infrared light. Carbon disulfide
is a colorless liquid transparent to both infrared and visible. Iodine
readily dissolves in this liquid and causes the liquid to turn a black color and to become completely opaque to visible light, given enough iodine. At the same time, however, the iodine has essentially no effect on the transparency of the liquid with respect to infrared light. Hence when light from an ordinary lightbulb is passed through a body of this solution, lots of infrared and only infrared emerges out at the other side. This infrared light can be brought to a focus with a concave mirror (or an optical lens made from rock-salt, but not a lens made from glass because glass is a poor transmitter of infrared). At the point of focus, with a good focusing tool, the infrared beam is strong enough to set paper on fire. If a little piece of non-combustible solid material is placed at the focus, it will glow visibly in the heat; i.e. the material will absorb infrared and emit visible light.
The following is another laboratory illustration of calorescence. In a flame of pure hydrogen
burning in oxygen, the hydrogen chemically combines with the oxygen to form water (H2O) plus a lot of heat is produced. This heat is a radiant emission from the newly formed water molecules. That is, the heat is thermal radiation whose particular set of radiant frequencies is uniquely characteristic of water molecules, as determined by emission spectroscopy. Water molecules have very little emission in the visible portion of the spectrum at any temperature (c.f. spectral absorption of water
). The temperature of the hydrogen flame is more than 2000 degrees Celsius. If a piece of platinum
is placed in the flame, the platinum will become "white hot" and give out a bright light. The platinum thus absorbs radiation having the spectral profile of water, and emits radiation having the spectral profile of platinum. (The platinum also picks up heat from collisions with moving gas molecules).
The term calorescence is rarely seen in use today, whereas the term fluorescence is common. One reason is that there isn't a physical explanation for calorescence that's specific to calorescence. Relatedly, the physical explanations for some types of fluorescence behavior are also explanations for calorescence and the word fluorescence has been preferred and expanded in customary usage to include calorescence. Another reason is that there isn't a widely used practical application attached to the word calorescence, whereas there is for fluorescence. A related item of physics terminology today is the so-called "Anti-Stokes Shift
". A Stokes shift refers to molecular absorptions of radiant energy of higher frequencies followed by emissions of lower frequencies; and an anti-Stokes shift refers to absorptions of lower frequencies followed by emissions of higher frequencies. With this terminology, practical applications are attached to the term "anti-Stokes photoluminescence" in materials science including semiconductors (see examples). Equal terminology in use in laser science is "infrared upconversion", "upconversion luminescence", or simply "upconversion
" (see examples). This terminology is usually contemplating luminescence
, as opposed to incandescence
, whereas the word Calorescence belongs to the 19th century when the only known upconversion methods were of the incandescent kind.
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
radiant energy and emits visible radiant energy in its place. For example, some kinds of flammable gas give off large amounts of radiant heat and very little visible light when burning, and if a piece of metal is placed into such a flame, the metal will become bright red-hot—which is to say the metal absorbs invisible infrared and emits visible radiation. The word calorescence was coined in 1864 on the model of the word fluorescence
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
which had been coined in 1852. At that time, fluorescence was defined as absorption in the ultraviolet part of the spectrum followed by emission in the visible part of the spectrum. Calorescence was defined complementarily as absorption in the infrared followed by emission in the visible.
The following is a laboratory demonstration of calorescence. An ordinary lightbulb emits lots of infrared light. Carbon disulfide
Carbon disulfide
Carbon disulfide is a colorless volatile liquid with the formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent...
is a colorless liquid transparent to both infrared and visible. Iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
readily dissolves in this liquid and causes the liquid to turn a black color and to become completely opaque to visible light, given enough iodine. At the same time, however, the iodine has essentially no effect on the transparency of the liquid with respect to infrared light. Hence when light from an ordinary lightbulb is passed through a body of this solution, lots of infrared and only infrared emerges out at the other side. This infrared light can be brought to a focus with a concave mirror (or an optical lens made from rock-salt, but not a lens made from glass because glass is a poor transmitter of infrared). At the point of focus, with a good focusing tool, the infrared beam is strong enough to set paper on fire. If a little piece of non-combustible solid material is placed at the focus, it will glow visibly in the heat; i.e. the material will absorb infrared and emit visible light.
The following is another laboratory illustration of calorescence. In a flame of pure hydrogen
Hydrogen fuel
An ecologically-friendly fuel which uses electrochemical cells or combusts in internal engines to power vehicles and electric devices. It is also used in the propulsion of spacecraft and can potentially be mass produced and commercialized for passenger vehicles and aircraft.In a flame of pure...
burning in oxygen, the hydrogen chemically combines with the oxygen to form water (H2O) plus a lot of heat is produced. This heat is a radiant emission from the newly formed water molecules. That is, the heat is thermal radiation whose particular set of radiant frequencies is uniquely characteristic of water molecules, as determined by emission spectroscopy. Water molecules have very little emission in the visible portion of the spectrum at any temperature (c.f. spectral absorption of water
Water absorption
During the transmission of electromagnetic radiation through a medium containing water molecules, portions of the electromagnetic spectrum are absorbed by water molecules...
). The temperature of the hydrogen flame is more than 2000 degrees Celsius. If a piece of platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
is placed in the flame, the platinum will become "white hot" and give out a bright light. The platinum thus absorbs radiation having the spectral profile of water, and emits radiation having the spectral profile of platinum. (The platinum also picks up heat from collisions with moving gas molecules).
The term calorescence is rarely seen in use today, whereas the term fluorescence is common. One reason is that there isn't a physical explanation for calorescence that's specific to calorescence. Relatedly, the physical explanations for some types of fluorescence behavior are also explanations for calorescence and the word fluorescence has been preferred and expanded in customary usage to include calorescence. Another reason is that there isn't a widely used practical application attached to the word calorescence, whereas there is for fluorescence. A related item of physics terminology today is the so-called "Anti-Stokes Shift
Stokes shift
Stokes shift is the difference between positions of the band maxima of the absorption and emission spectra of the same electronic transition. It is named after Irish physicist George G. Stokes. When a system absorbs a photon, it gains energy and enters an excited state...
". A Stokes shift refers to molecular absorptions of radiant energy of higher frequencies followed by emissions of lower frequencies; and an anti-Stokes shift refers to absorptions of lower frequencies followed by emissions of higher frequencies. With this terminology, practical applications are attached to the term "anti-Stokes photoluminescence" in materials science including semiconductors (see examples). Equal terminology in use in laser science is "infrared upconversion", "upconversion luminescence", or simply "upconversion
Photon upconversion
Photon upconversion is a process in which the sequential absorption of two or more photons leads to the emission of light at shorter wavelength than the excitation wavelength. It is a anti-Stokes type emission. An example is the conversion of infrared light to visible light. Materials by which...
" (see examples). This terminology is usually contemplating luminescence
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
, as opposed to incandescence
Incandescence
Incandescence is the emission of light from a hot body as a result of its temperature. The term derives from the Latin verb incandescere, to glow white....
, whereas the word Calorescence belongs to the 19th century when the only known upconversion methods were of the incandescent kind.