Optical bands of F2 and centers in LiF

Baldacchini, G.; Nicola, E. De; Montereali, Rosa Maria; Scacco, A.; Калинов, В. С.

doi:10.1016/s0022-3697(99)00236-x

Cited by 100 publications

(59 citation statements)

References 13 publications

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“…We stress that the non-radiative decay channels are almost completely quenched for both PL signals at the temperature at which the experiments were performed (25 K). 13,22 As a consequence, it is a very good approximation to consider the luminescence decay to be purely radiative. The main point of the following discussion is to fit all experimental data by our model and extract the values of the homogeneous and inhomogeneous widths of the PL emission bands and other interesting physical parameters.…”

Section: Discussionmentioning

confidence: 99%

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

et al. 2008

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The article describes an experimental method that allows to estimate the inhomogeneous and homogeneous linewidths of the photoluminescence band of a point defect in an amorphous solid. We performed low temperature time-resolved luminescence measurements on two defects chosen as model systems for our analysis: extrinsic Oxygen Deficient Centers (ODC(II)) in amorphous silica and F + 3 centers in crystalline Lithium Fluoride. Measurements evidence that only defects embedded in the amorphous matrix feature a dependence of the radiative decay lifetime on the emission energy and a time dependence of the first moment of the emission band. A theoretical model is developed to link these properties to the structural disorder typical of amorphous solids. Specifically, the observations on ODC(II) are interpreted by introducing a gaussian statistical distribution of the zero phonon line energy position. Comparison with the results obtained on F + 3 crystalline defects strongly confirms the validity of the model. By analyzing experimental data within this frame, we obtain separate estimations of the homogenous and inhomogeneous contributions to the measured total linewidth of ODC(II), which results to be mostly inhomogeneous.

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Section: Discussionmentioning

confidence: 99%

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

et al. 2008

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“…The main absorption bands (F,M) are of similar magnitude in the two samples. However, the spectra differ in the F 4 region and also, as we had already indicated, in the relative contributions of the F 2 and F 3 + centers to the M band, which may be inferred from the different linewidths of the M band for the two crystals [15].…”

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confidence: 55%

“…We report here results for two crystals colored at room temperature (RT), one of which was used as such (sample A), while the other one was annealed at 200 °C for about 20 min and then quickly cooled to RT (sample B). It was previously shown [15] that this annealing decreases the concentration of F 3 + centers with respect to F 2 centers. Results for crystals irradiated at -60 °C had been reported earlier (samples C and D; the D sample received an additional optical bleaching at 308 nm) [5][6][7].…”

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confidence: 87%

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Thermoluminescence of LiF and F₂ color centers

Baldacchini

Davidson

Калинов

et al. 2007

Phys. Status Solidi (c)

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Light emitted when heating crystalline materials previously exposed to ionizing radiation is commonly known as thermoluminescence. The resultant glow curve is related to the material, the impurities and the defect centers generated by the irradiation. Several efforts have been made in the past to associate glow peaks with specific defect centers. Recently, in the case of LiF we established a link between F 3 + and F 3 centers and the temperature region of the glow curve below 200 °C. This result was obtained by using especially treated samples with known concentration of color centers in first place, and annealing measurements in second place. By continuing these studies, it has been possible to establish a further link between F 2 centers and a prominent feature of the glow curve near 260 °C. Although it is known that irradiated alkali halides release thermal energy when they are heated above the irradiation temperature, the inner mechanisms of the phenomenon is still the subject of debate. This is mostly due to the large number of the processes involved. Physical models of TL have been proposed by various authors [1][2][3]. The general scheme admits a discrete number of localized levels in the forbidden energy gap between the valence and conduction bands. Several levels below the bottom of the conduction band serve as electron traps, and by analogy several trapping levels for positive holes are assumed to be present above the valence band.On warming up the crystal, trapped carriers are being released from the localized levels, and recombine with trapped carriers of opposite sign. The crux of the TL debate is about the nature of the mobile entities which can be electrons or holes according to the Mayhugh model [2] or are interstitial halogen atoms according to the Spanish group of Alvarez Rivas [3]. The recombination process may be accompanied by the emission of photons in a series of glow peaks which contribute to the formation of the TL curve. In this connection the first step toward a basic understanding of the TL mechanism depends on the identification of the trapping and recombination centers. Electrons and holes trapped at defects, impurities and vacancies in the crystal normally introduce optical absorption (color centers, CCs) into the transparent crystal, because the defect energy levels lie in the forbidden gap of the of the insulating crystal. Therefore the filling and emptying of the TL traps should correlate with changes in the optical absorption bands, which can give information about the TL processes.

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“…The F 2 and F 3 + color centers make up the so-called "M" absorption band, and re-emit at 670 and 539 nm respectively. 10 There are several weaker visible absorption bands due to more complex aggregate centers called "R" centers. Irradiated LiF also produces luminescence due to recombination of excitons.…”

Section: Spectrally and Temporally Resolved Trdmentioning

confidence: 99%

Transient Radiation Darkening Features in VISAR Window

Stevens¹,

Moy²

2001

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Optical bands of F2 and centers in LiF

Cited by 100 publications

References 13 publications

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

Thermoluminescence of LiF and F₂ color centers

Transient Radiation Darkening Features in VISAR Window

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Optical bands of F2 and centers in LiF

Cited by 100 publications

References 13 publications

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time-resolved emission spectroscopy

Thermoluminescence of LiF and F2 color centers

Transient Radiation Darkening Features in VISAR Window

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Thermoluminescence of LiF and F₂ color centers