Multiple emission wavelengths

Due to space limitations, we can only make brief mention of DAS and lifetime distributions. DAS (decay associated spectra) are the emission spectra associated with the different decay species and are described in (11). Examples of applications may be found in (12-14). The treatment of fluorescence lifetimes as distributions (rather than as the discrete values implied in Section 2.1) is discussed in (15-18). Commercially available software packages (see Section 2.6.1) are typically able to carry out the necessary analysis to obtain DAS ftom decay measurements made at multiple emission wavelengths, or to obtain lifetime distributions. 

EFFECTS OF SUMMING SIGNALS FROM MULTIPLE EMISSION WAVELENGTHS FROM AN ELEMENT ON THE UMIT OF DETECTION AND SENSITIVITY... 

In practice, a multiplication factor C must be introduced to take into account the experimental conditions (total concentration, choice of excitation and emission wavelengths, bandpasses for absorption and emission intensity of the incident light, sensitivity of the instrument). 

The tail of the plasma formed at the tip of the torch is the spectroscopic source, where the analyte atoms and their ions are thermally ionized and produce emission spectra. The spectra of various elements are detected either sequentially or simultaneously. The optical system of a sequential instrument consists of a single grating spectrometer with a scanning monochromator that provides the sequential detection of the emission spectra lines. Simultaneous optical systems use multichannel detectors and diode arrays that allow the monitoring of multiple emission lines. Sequential instruments have a greater wavelength selection, while simultaneous ones have a better sample throughput. The intensities of each element s characteristic spectral lines, which are proportional to the number of element s atoms, are recorded, and the concentrations are calculated with reference to a calibration standard. 

Figure 141 shows the EL spectra from a microcavity (a) and conventional LED (b) based on the emission from an NSD dye forming a thin emitting layer of a three-organic layer device. It is apparent that the half-width of emission spectra from the diode with microcavity is much narrower than those from the diode without cavity. With 0 = 0°, for example, the half-width of the spectrum of the diode with cavity is 24 nm whereas that of the sample without cavity increases to 65 nm. According to Eq. (275), the resonance wavelength, A, decreases with an increase of 0 in agreement with the experimental data of Fig. 141. We note that no unique resonance condition in the planar microcavity is given due to broad-band emission spectrum of the NSD emission layer. Multiple matching of cavity modes with emission wavelengths occurs. Thus, a band emission is observed instead a sharp emission pattern from the microcavity structure as would appear when observed with a monochromator the total polychromic emission pattern is a superposition of a range of monochromatic emission patterns. The EL spectra...

The emission quantum yields are strongly wavelength dependent but are always within the range of the quantum yields of Rh(bipy)33 and Rh(phen)33 " (Table 8). The multiple emission properties of these complexes have been interpreted in terms of exciton states which are localized on the individual ligand molecules. 

The emission spectra of a phosphor can have multiple distinct wavelength peaks. As stated earlier, the emission level of these peaks can change with temperature. For instance. Fig. 1 shows the emission spectra of La202S Each emission line is characterized... 

Figure 1 shows the fluorescence excitation and emission spectra of 1 in CH2CI2. The excitation spectrum was found to be independent of the monitoring wavelengths and was identical to the absorption spectrum. Three emission bands at Xp 645, 660 and 702 nm are observed in the emission spectrum and they are designated as the a-, the j5- and the y-band respectively. Controlled experiments showed that the multiple emission is from 1 rather than from any impurities or any aggregational states of 1. 

The fluorescence intensities at each wavelength (430, 505, 570, and 660 ran) and absorbance (280 nm) of the fraction are depicted in Fig. 1. Multiple emissions were observed at one excitation wavelength 298 nm. Fluorescent spectra of Fr (2-10) and Fr (3-6) were examined at different sodium chloride concentrations. Emission peaks were observed at 430 480, 505, 570, 636 and 663 nm. The remarkable result was that the 570 nm emission peak only appeared in 0.15M-NaCl (Fig. 2). pH dependency of the fluorescent spectra were analyzed by changing the pH from 7.0 to 8.5. Results are shown in Fig. 3. 

Fig. 1. Fluorescent intensities of each wavelength from the anion exchange column fractions (Q-Sepharose). Multiple emissions were observed at one excitation wavelength (298 nm) using a spectrofluorophotometer, 10 mM-Tris buffer pH 8.5, and changing sodium chloride concentration 0.1 M to 0.15 M.

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