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and is crucial for the light emission. Oxidation of the activator is one of the common mechanisms of phosphor degradation. The distribution of the activator in the crystal is also of high importance.
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are effective. The holes associated with electrons in the conduction band are independent from the latter. Those holes and electrons are captured successively by impurity centers exciting certain
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The activator is the main factor determining the phosphor emission wavelength. The nature of the host crystal can however to some degree influence the wavelength as well.
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until they are captured as a whole by impurity centers. The latter then rapidly de-excite by emitting scintillation light (fast component). In case of inorganic
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of the ions can cause depletion of the crystal from the activators with resulting loss of efficiency. This is another mechanism of phosphor degradation.
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Dixie, Laura
Catherine; Edgar, Andrew; Bartle, Colin Murray (2014). "Samarium doped calcium fluoride: A red scintillator and X-ray phosphor".
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not accessible to the excitons. The delayed de-excitation of those metastable impurity states, slowed by reliance on the low-probability
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Nuclear
Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
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can play the role of the impurity.) The wavelength emitted by the emission center is dependent on the atom itself, its
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The activators prolong the emission time (afterglow). In turn, other materials (such as
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in the red region of the spectrum, particularly when cooled by dry ice.
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The electronic configuration of the activator depends on its
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of the material to create desired type of nonhomogeneities.
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414:2014NIMPA.753..131D
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