Absorption, excitation, and emission spectra

Figure 5.7 Room-temperature electronic absorption, excitation and emission spectra for 2 in aqueous solution. The excitation spectrum of 2 was recorded by monitoring emission at 400 nm. Reproduced with permission from [31]. Copyright (2004) Royal Society of Chemistry.

Representative absorption (excitation) and emission spectra of a fluoro-chrome are provided in Fig. 1. Some degree of overlap between the two spectra is typical, and often the excitation and emission spectra are mirror images of each other. The separation between the wavelengths at which excitation and emission maxima occur is referred to as the Stokes shift. 

Cu Y. The absorption, excitation, and emission spectra of the Cu Y specimen were reported earlier (4, 10). The emission line is a perfect Gaussian centered at 18400 cm-- - (543 nm) of... 

Table 2.4 Peak positions of the absorption, excitation and emission spectra of the alkaline earth oxides.

Representative absorption (excitation) and emission spectra of a fluorochrome are provided in Fig. 1. Some degree of overlap... 

Pan Z, Ning L, Cheng B-M, Tanner PA (2006) Absorption, excitation and emission spectra of SrCl2 Eu L Chem Phys Lett 428 78-82... 

Luminescent Properties The (La, Tb)P04 phosphor has very weak absorption lines at the ultraviolet region, but by adding Ce " this phosphor results in a remarkable increase in absorption and emission intensity because Ce " can act as an efficient sensitizer to Tb ". The absorption, excitation, and emission spectra are shown in Fig. 8.4a. As presented, the absorption and excitation spectrum shows a broad band in UV region with a dominant peak at approximately 280 nm. The emission spectmm remains the characteristic emission peak of Tb " with a dominant peak at 543 nm. Similar to (Ce, Tb)MgAlnOi9, energy transfer from Ce " to... 

Fig. 8.4 a Absorption, excitation and emission spectra of (La, Ce, Tb)P04. Reprinted with permission from reference [20]. Copyright 2000 American Chemical Society, b Effects of fluxes on luminance of (La, Ce, Tb)P04 [19]... 

Photophysical Processes in Dimethyl 4,4 -Biphenyldicarboxy-late (4,4I-BPDC). The ultraviolet absorption spectrum of dimethyl 4,4 -biphenyldicarboxyl ate was examined in both HFIP and 95% ethanol. In each case two distinct absorption maxima were recorded, an intense absorption near 200 nm and a slightly less intense absorption near 280 nm. The corrected fluorescence excitation and emission spectra of 4,4 -BPDC in HFIP at 298°K shows a single broad excitation band centered at 280 nm with a corresponding broad structureless emission band centered at 340 nm. At 77°K, the uncorrected phosphorescence spectra shows a single broad structureless excitation band centered at 298 nm, and a structured emission band having maxima at 472 and 505 nm with a lifetime, t, equal to 1.2 seconds. 

The excitation spectrum of a molecule is similar to its absorption spectrum, while the fluorescence and phosphorescence emission occur at longer wavelengths than the absorbed light. The intensity of the emitted light allows quantitative measurement since, for dilute solutions, the emitted intensity is proportional to concentration. The excitation and emission spectra are characteristic of the molecule and allow qualitative measurements to be made. The inherent advantages of the techniques, particularly fluorescence, are ... 

In order to select the operating conditions for any fluorimetric method, the excitation and emission spectra of the analyte must be determined. Figure 2.9 illustrates the fact that an emission spectrum is an approximate mirror image of the excitation spectrum, the latter being similar to the absorption spectrum of the compound. 

EXAMPLE 1.4 Consider a phosphor with a three energy level scheme and the absorption spectrum shown in Figure 1.9(a). Assuming similar transition probabilities among these levels, discuss the nature of the excitation and emission spectra and their relationship to the absorption spectrum. 

Compounds 1,2,3,5,10,11,12,13,14 were dissolved in EPIP (diethyl ether, petroleum ether, isopropanol 5 5 2)whereas compounds 4,6,7,8,9,15 were dissolved in THF-DE (tetrahydrofurane, diethyl ether 1 1). These solvent mixtures can be frozen as glassy samples at 77 K. The absorption spectra were recorded on a standard spectrophotometer SF-10 or Beckman-5270. The measurements of fluorescence excitation and emission spectra were made with the aid of a spectrofluorometer SLM-4800 with automatic correction of spectral response. Fluorescence lifetimes were measured with the aid of a pulse fluorometer PRA-3000. Magnetic circular dichroism (MCD) measurements were carried out in a 8 kG magnetic field using a JASCO J-20 circular dichrometer. Triplet state formation was observed for investigated compounds at the experimental set up, whose detailed description can be found in our paper (27). The optical experiments were carried out with a porphyrin concentration of 4.10- - 4.10 mol.l". In NMR investigations (Bruker WM-360) we used higher concentrations ( 5.10" raol.l ) and dried solvents (CDCl, C 2 and toluene-d0). 

Electronic absorption and fluorescence excitation and emission spectra of phenazines were determined in several solvents of various polarities <1995SAA603>, and the effect of the solvent upon the spectral characteristics was studied. 

The complex is luminescent in the solid state and in solution in pyridine. The absorption spectrum shows a maximum at 340 nm and the emission spectrum displays a band at 425 nm. The crystals are also luminescent, but the excitation and emission spectra appear at different wavelengths. Thus, the complex emits at 490 nm and the excitation spectrum is complicated, with bands in a wide range from 300 to 450 nm. This result suggests that different species are responsible for luminescence in the solid state and in solution, with the isolated trinuclear complex being the emitting species in solution, while the luminescent properties of the crystal are the result of the extended supramolecular aggregation in the solid. As before, the complex did not exhibit solvoluminescence. 

Figure 18-21 Excitation and emission spectra of anthracene have the same mirror image relation as the absorption and emission spectra in Figure 18-16. An excitation spectrum is nearly the same as an absorption spectrum. [C. M. Byron and T. C. Wemer. Experiments in Synchronous Fluorescence Spectroscopy lor the Undergraduate Instrumental Chemistry Course"...

Visible and ultraviolet absorption and room temperature fluorescence excitation and emission spectra obtained from alcoholic... 

The electropolymerization of 3-methoxythiophene (MOT) was performed in an aqueous micellar medium containing sodium dodecylsulfate (SDS) as a surfactant. The electronic absorption spectra, the fluorescence excitation and emission spectra, and the quantum yields of 546, were measured in different solvents of various polarities and hydrogen bond abilities (89SM(28)C487 98SM(93)175 00JF107 00POLLDG4047 ... 

A simple, rapid, sensitive, and selective spectrofluorimetric method (2ex/ lem = 345/455nm) has been developed for the determination of zaleplon. Tang et al. have studied the influence of micellar medium on the absorption, fluorescent excitation, and emission spectra character of zaleplon The nonionic surfactant of Triton X-100 showed a strong sensitizing effect for the fluorescence of zaleplon in a pH 5.0 buffer. The possible enhancement mechanism was discussed. Based on the optimum conditions, the linear range was 1.32 x 10 8-1.00 x 10 mol/1. The detection limit was 4.0 x 10 mol/1 with a relative standard deviation (RSD) of 0.06%. The proposed method was successfully applied to the determination of zaleplon in tablets, serum, and urine. 

The energy transfer efficiency is directly proportional to the spectral overlap, and this also directly affects the Forster distance of a particular D-A pair. Figure 10.5 shows the D and A excitation and emission spectra in an ideal energy transfer system, wherein D and A have very distinct excitation spectra (so that A can only be excited by energy transfer and not by direct photon absorption at the wavelengths used to excite D)—the D emission and A excitation spectra overlap strongly—and the D and A emission maxima are well separated, so that the quenching of D fluorescence and the enhancement of A fluorescence can be individually measured.98 99... 

Analytical absorption spectroscopy in the ultraviolet and visible regions of the elechomagnetic spectrum has been widely used in pharmaceutical and biomedical analysis for quantitative purposes and, with certain limitations, for the characterisation of drugs, impurities, metabolites, and related substances. By contrast, luminescence methods, and fluorescence spectroscopy in particular, have been less widely exploited, despite the undoubted advantages of greater specificity and sensitivity commonly observed for fluorescent species. However, the wider availability of spectrofluorimeters capable of presenting corrected excitation and emission spectra, coupled with the fact that reliable fluorogenic reactions now permit non-fluorescent species to be examined fluorimetrically, has led to a renaissance of interest in fluorimetric methods in biomedical analysis. 

Ono and Ware"" have measured the absorption, emission, and excitation spectra, the fluorescence decay times, and the quantum yields of a series of substituted diphenylmethylenes in rigid matrices at low temperatures. Acean-thrylene shows S2- So emission in hexane with a yield of 0.017 and lifetime of 4.3 ns. The low-temperature fluorescence spectra of bis-2-naphthyl-alkanes and their derivatives have been studied. Excimer formation is an activated process. The fluorescence and absorption spectra of 1,1-diphenyl-ethylenes have been analysed in some detail by Gustav and Bolke. " The S — Si transitions in trans isomers of phenylnaphthylethylenes have been assigned by picosecond absorption spectroscopy. Effects of solvent viscosity and the role of conformers in the mechanism of isomerization are elucidated. The production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K due to restrictions imposed by the solid matrix has also been reported. Free jet excitation and emission spectra of diphenyl-butadiene show clearly the lowest excited Ag state and give a lifetime of 52.8 ns for 0-0 excitation.Electric field-induced charges in the optical... 

Polymeric Systems.—Absorption, fluorescence excitation, and emission spectra of soluble poly(diacetylene) at room and liquid nitrogen temperature has been recorded for different solvents. The excimer-to-monomer emission ratio for polystyrene depends upon the polymer molecular weight but is independent of the solvent. Monolayer films of the 27-carbon-chain-length alkyldiace-... 

Figure 5.19. Absorption (A) and emission spectra (F and P) of phenanthrene in ethanol at 93 K. FP and PP denote the polarization spectra of fluorescence and phosphorescence, AP(F) and AP(P) the excitation polarization spectra of fluorescence and phosphorescence, respectively (by permission from D6rr, 1966).

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