NEW: Candoluminescence

Results: 3

Select item 37175881.

Determination of antimony in urine by candoluminescence spectrometry.

Clark ER, Patel M.

Analyst. 1986 Apr;111(4):415-7. No abstract available.

PMID:

 

3717588

Similar articles

Select item 189619472.

Candoluminescence-a new flame technique for trace analysis-II Determination of nanogram amounts of manganese.

Belcher R, Karpel S, Townshend A.

Talanta. 1976 Sep;23(9):631-5.

PMID:

 

18961947

Similar articles

Select item 189611543.

Candoluminescence-a new flame technique for trace analysis-I Development of a method for determination of bismuth.

Belcher R, Bogdanski S, Townshend A.

Talanta. 1972 Sep;19(9):1049-58.

PMID:

 

18961154

Candoluminescence

From Wikipedia, the free encyclopedia

Candoluminescence is the light given off by certain materials at elevated temperatures (usually when exposed to a flame) that has an intensity at some wavelengths which can be higher than the blackbody emission expected from incandescence at the same temperature.[1] The phenomenon is notable in certain transition metal and rare earth metal oxide materials (ceramics) such as zinc oxide and cerium oxide or thorium dioxide.

Contents

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History[edit]

The existence of the candoluminescence phenomenon and the underlying mechanism have been the subject of extensive research and debate since the first reports of it in the 1800s. The topic was of particular interest before the introduction of electric lighting, when most artificial light was produced by fuel combustion. The main alternative explanation for candoluminescence is that it is simply “selective” thermal emission in which the material has a very high emissivity in the visible spectrum and a very weak emissivity in the part of the spectrum where the blackbody thermal emission would be highest; in such a system, the emitting material will tend to retain a higher temperature because of the lack of invisible radiative cooling. In this scenario, observations of candoluminescence would simply have been underestimating the temperature of the emitting species. Several authors in the 1950s came to the view that candoluminescence was simply an instance of selective thermal emission, and one of the most prominent researchers in the field, V.A. Sokolov, once advocated eliminating the term from the literature in his noted 1952 review article,[2] only to revise his view several years later.[1] The modern scientific consensus is that candoluminescence does occur, that it is not always simply due to selective thermal emission, but the mechanisms vary depending on the materials involved and the method of heating, particularly the type of flame and the position of the material relative to the flame.[1]

Mechanism[edit]

When the fuel in a flame combusts, the energy released by the combustion process is deposited in combustion products, usually molecular fragments called free radicals. The combustion products are excited to a very high temperature called the adiabatic flame temperature (that is, the temperature before any heat has been transferred away from the combustion products). This temperature is usually much higher than the temperature of the air in the flame or which an object inserted into the flame can reach. When the combustion products lose this energy by radiative emission, the radiation can thus be more intense than that of a lower temperature blackbody which has merely been inserted into the flame. The exact emission process involved varies with the material, the type of fuels and oxidizers, and the type of flame, though in many cases it is well established that the free radicals undergo radiative recombination.[3] This energetic light emitted directly from the combustion products may be observed directly (as with a blue gas flame), depending on the wavelength, or it may then cause fluorescence in the candoluminescent material. Some free radical recombinations emit ultraviolet light, which is only observable through fluorescence.

One important candoluminescence mechanism is that the candoluminescent material catalyzes the recombination, enhancing the intensity of the emission.[1] Extremely narrow wavelength emission by the combustion products is often an important feature in this process, because it reduces the rate at which the free radicals lose heat to radiation at invisible or non-fluorescence-exciting wavelengths. In other cases, the excited combustion products are thought to directly transfer their energy to luminescent species in the solid material. In any case, the key feature of candoluminescence is that the combustion products lose their energy to radiation without becoming thermalized with the environment, which allows the effective temperature of their radiation to be much higher than that of thermal emission from materials in thermal equilibrium with the environment.

Welsbach lights[edit]

Early in the 20th century, there was vigorous debate over whether candoluminescence is required to explain the behavior of Welsbach gas mantles or limelight. One counterargument was that since thorium oxide (for example) has much lower emissivity in the near infrared region than the shorter wavelength parts of the visible spectrum, it should not be strongly cooled by infrared radiation, and thus a thorium oxide mantle can get closer to the flame temperature than can a blackbody material. The higher temperature would then lead to higher emission levels in the visible portion of the spectrum, without invoking candoluminescence as an explanation.[4]

Another argument was that the oxides in the mantle might be actively absorbing the combustion products and thus being selectively raised to combustion-product temperatures.[5]Some more recent authors seem to have concluded that neither Welsbach mantles nor limelight involve candoluminescence (e.g. Mason[3]), but Ivey, in an extensive review of 254 sources,[1] concluded that catalysis of free radical recombination does enhance the emission of Welsbach mantles, such that they are candoluminescent.

See also[edit]

References[edit]

  1. ^Jump up to:a b c d e F. Ivey, “Candoluminescence and radical-excited luminescence,” Journal of Luminescence 8:4, pp. 271–307 (1974)
  2. Jump up^Соколов В. А. (1952). “Кандолюминесценция (Candoluminescence)” (PDF). Успехи физических наук (Russian Journal of Physics). XLVII (4): 537–560. ISSN 0042-1294.
  3. ^Jump up to:a b M. Mason, “Candoluminescence” in Proc. Am. Chem. Soc., Div. Fuel Chem., V. 11:2, pp. 540-554,(1967)
  4. Jump up^us 4539505, A. Riseberg, Leslie, “Candoluminescent electric light source”, issued 3 Sep 1985 (Note however that patents are not peer reviewed sources.)
  5. Jump up^Comment by P. Steinmetz to H.E. Ives and W.W. Coblentz, “The Light of the Firefly” in Transactions of the Illuminating Engineering Society V.4, p. 677-679, (1909)

Кандолюминесценция

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Материал из Википедии — свободной энциклопедии

Кандолюминесценция (лат. cando- — корневая основа англ. incandescent — накалённый добела, от лат. incandesco — раскаляться) — люминесценция, возбуждаемая при рекомбинации радикалов на поверхности[1]. Именуется также «калильным свечением», «температурной люминесценцией» или «люминесценцией накалённых тел». Проявляется в виде избыточной видимой светимости сверх теплового равновесного излучения за счет переноса энергии из невидимой части спектра.

Примером такой люминесценции может служить так называемый друммондов свет — избыточная светимость CaO при нагревании[2].

Явление кандолюминесценции используется в калильных сетках для керосиновых и газовых ламп. Основа сеток — смесь оксидов тория и церия.

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Примечания[править | править вики-текст]

  1. ↑http://www.ijs.speleo.it/pdf/72.593.39(1)_Sweet.et.al.pdf
  2. ↑Соколов В. А. Кандолюминесценция // Успехи физических наук. — М., 1952. — Т. XLVII, вып. 4. — С. 537—560. — ISSN 0042-1294.