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sxy5306铁杆木虫 (著名写手)
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| Fluorescence，luminescence，photoluminescence的主要区别是什么？ |
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wenyun0876
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2楼2009-10-09 07:57:53
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hitechceram(金币+2,VIP+0): 10-12 11:44
hitechceram(金币+2,VIP+0): 10-12 11:44
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Fluorescence is the emission of visible light by a substance that has absorbed light of a differing, usually invisible, wavelength. Absorption of a photon triggers the emission of a photon with a longer (less energetic) wavelength. A shorter wavelength emission is sometimes observed from multiple photon absorption. The energy difference between the absorbed and emitted photons ends up as molecular rotations, vibrations or heat. Sometimes the absorbed photon is in the ultraviolet range, and the emitted light is in the visible range, but this depends on the characteristics of the particular fluorescent substance. Luminescence is light that usually occurs at low temperatures, and 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 generated by high temperatures. Historically, radioactivity was thought of as a form of "radioluminescence", although it is today considered to be separate since it involves more than electromagnetic radiation. Photoluminescence (abbreviated as PL) is a process in which a substance absorbs photons (electromagnetic radiation) and then re-radiates photons. Quantum mechanically, this can be described as an excitation to a higher energy state and then a return to a lower energy state accompanied by the emission of a photon. This is one of many forms of luminescence (light emission) and is distinguished by photoexcitation (excitation by photons), hence the prefix photo-.[1] The period between absorption and emission is typically extremely short, in the order of 10 nanoseconds. Under special circumstances, however, this period can be extended into minutes or hours. |
4楼2009-10-12 11:08:12
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