Temperature-dependent emission spectra

Figure 5.2 Temperature-dependent emission spectra of [(TPA) AuClj (a) 78 K (b) 200 K (c) 250 K. Emission is quenched at room temperature. The excitation spectrum was recorded at 78 K. Reproduced with permission from [22]. Copyright (1995) American Chemical Society.

Figure 7. Temperature-dependent emission spectra for 10 /xM PRODAN in CF3H.

Kim IS, Park YH, Kim SM, Choi JC, Park HL (2005) Temperature-dependent emission spectra of M2Si04 Eu (M = Ca, Sr, Ba) phosphors for green and greenish white LEDs. Solid State Comm 133 445... 

Fig. 2.15 Temperature-dependent emission spectra of the optimized BMAS 4%Eu, 8%Tb, 16%Mn sample. Reprinted with the permission from Ref. [28]. Copyright 2011 American Chemical Society...

Fig. 13.2 a Temperature-dependent emission spectra of NaBaScSi207 0.01Eu from 30 to 300 °C at 365 nm excitation and b comparison of the relative intensities of NaBaScSi207 0.01Eu and commercial Ba2Si04 Eu, as well as the emission peaks of NaBaScSi207 0.01Eu, all as a function of temperature. Reproduced from Ref. [4] by permission of The Royal Society of Chemistry... 

Li et al. also reported the colloidal synthesis of Co-doped CdSe nanowires by the SLS strategy using the same reactants, except (MnSt)2 was replaced by cobalt stearate (CoSt)2 and the injection temperature was increased to 280°C. As-grown Co Cdi. Se (x = 0.3%) NWs were of 17.7 1.9nm in diameter and 1.8 0.2 pm in length with Bi catalysts located on both NW ends which demonstrated the SLS growth mechanism. The admixture of zinc blende and wurtzite structures were observed from TEM images. The diameter of the NWs can be tailored between 8 to 30 nm and the Co concentration can be tuned from 0 to 2.1% by varying the concentration of the reactants and reaction temperature. The temperature-dependent emission spectra of the Co-doped CdSe NWs were blue-shifted with increase of... 

Fig. 3.6 Temperature-dependent emission spectra of a [Tb(hfa)3(dpbp)] . b TbCNOala, and c [Eu(hfa>3(dpbp)] in the solid state in the temperature range of 200-300 K = 380 nm)...

Since 1 and 2 usually depend on the wavelength of the emitted radiation and the temperature, the emission spectrum of the radiator and Q must be adjusted to each respective product state during the drying process. This is done in each section of the dryer, through which the product passes. 

Figure 4.10(b) shows the temperature dependence of the absorption spectrum expected for an indirect gap. It can be noted that the contribution due to becomes less important with decreasing temperature. This is due to the temperature dependence of the phonon density factor (see Equation (4.37)). Indeed, at 0 K there are no phonons to be absorbed and only one straight line, related to a phonon emission process, is observed. From Figure 4.10(b) we can also infer that cog shifts to higher values as the temperature decreases, which reflects the temperature dependence of the energy... 

Another example is the luminescence of in YPO4 with tetragonal zircon structure (Oomen et al. 1988). The emission consists of two bands, one in the UV region and one in the visible part of the spectrum. The intensity ratio of these bands is strongly temperature dependent (Fig. 5.57). 

The complexes exhibited different behavior in solution. The gold-thallium derivative showed a shift of the emission to 536 nm when the measurement was carried out in frozen solution. This was explained by a higher aggregation of [Aull(MTP)2] units in the solid state compared to the situation in solution. In the case of the Au-Pb compound, the emission spectrum showed a strong dependence on the aggregation state and temperature. Thus, the emission band in TH F solution, which appeared at 555 nm (298 K) (x = 57 ns), was shifted to 480 nm in frozen solution (x = 2.3 ps) or appeared at 752 nm in solid state (x = 22 ns). As with the thallium complex, the shift to high energy in solution may have been related to the polymeric structure of the complex in the solid state that was not reproduced in solution. 

In the delayed emission spectrum of eosin in glycerol or ethanol two bands are present, the relative intensities of which are strongly temperature-dependent (see Fig. 12). The visible band at 1.8 has a contour identical with that of the fluorescence band. It no doubt corresponds to the visible phosphorescence observed by Boudin.26 To interpret the results it was assumed that this band of delayed fluorescence was produced by thermal activation of the eosin triplet to the upper singlet level followed by radiative transition from there to the ground state. The far red band was assumed to correspond to the direct transition from the triplet level to the ground state and was therefore called phosphorescence. To determine the relationship between the intensities of the two bands we write the equations for the formation and consumption of triplet molecules as follows ... 

The ratio of the intensities of the two bands in delayed emission spectrum should thus be independent of the efficiency of triplet formation and of all triplet quenching processes. It should also be independent of the intensity of absorption Ia. The rate of emission is then given as Aed[T1 where Aed is temperature dependent. 

For recording of the emission spectrum, the emitted radiation is focussed on the slit of a monochromator and intensities measured attach wavelength. Since sensitivities of photocells or photomultipliers are wavelength dependent, a standardization of the detector-monochromator combination is necessary for obtaining true emission spectrum This can be done by using a standard lamp of known colour temperature whose emission characteristics is obtained from Planck s radiation law. The correction term is applied to the instrumental readings at each wavelength. Very often substances whose emission spectra have been accurately determined in the units of relative quanta per unit wavenumber intervals are... 

Experimentally, one is interested first of all in the order of the reaction, its absolute rate, and the temperature dependence of that rate. In addition to these primary data of chemical kinetics, one can observe the emission spectrum of ABC under various experimental conditions. From these observations one tries to infer information about the vibrational and electronic states involved, and their interactions, with or without collisions. Theoretically, interest centers on potential surfaces. Unfortunately, these are all too often thought of as potential curves, so that two of the three internal coordinates of the molecule are ignored. The experimental and theoretical difficulties are such that, even in terms of such an oversimplified model, it is seldom possible to arrive at a unique, widely agreed upon picture of the reaction process. 

As the temperature dependence of the CTL spectrum has information about the type of vapor, the present authors and coworkers [17] reported a method to recognize organic vapors by means of spectrum-temperature imaging. For this purpose, a system to simultaneously measure the CTL spectra at various temperatures was developed (Fig. 27). The sintered layer of the CTL catalyst is laid on a ceramic heater substrate of 5 x 60 mm2, which has a temperature distribution ranging from 440 to 530 °C along the stream of a sample gas in a quartz tube. A mask with an optical slit of 0.3 mm width is placed on a quartz tube. The CTL emission passing through the slit is focused on... 

The behavior of this complex in solution is interesting since its emission spectrum shows a strong dependence on the aggregation state and temperature. Thus the emission band in THF solution, which appears at 555 nm (298 K) (t = 57 ns), is shifted to 480 nm in frozen solution (t = 2.3 ps) or appears at 752... 

The temperature variation can affect not only the fluorescence intensity of the spectrum but also its emission bandwidth. However, this is dependent on the fluorophore environment and the fluorophore. Figure 10.17 shows the fluorescence emission spectrum of Trp residues of the protein LCA. In the range of temperatures studied, a shift to the red was not observed, and so we are far from denaturing temperatures. In addition, the emission bandwidth (54 nm) does not change with temperature. 

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