Fluorescence mirror image relation

Absorption and Emission Spectra. The excitation-emission spectrum of 1 (bottom half of Fig. 1) shows that the relatively narrow emission band is nearly independent of the excitation wavelength and that the excitation spectrum is not only nearly independent of the wavelength at which the emission is monitored, but is also very similar to the absorption spectrum, both being somewhat broader than the emission band. This leaves no doubt that the observed emission is due to the polysilane, and its shape, location and the mirror image relation to the absorption permit its assignment as fluorescence. 

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"...

Normalized steady state absorption and stimulated fluorescence spectra of cresyl violet in polar solvents are shown in Fig. 2. Stimulated spectra were calculated from the fluorescence spectra divided by the square of the wavenumber. Exciting wavelengths in each solvent used for the measurements are also indicated in the figure by arrows. Mirror image relation between... 

Another example of the mirror-image relation between absorption and fluorescence spectra is provided by anthracene (Figure 5.11). In this particular case the situation is complicated by vibronic coupling the L, and Lb bands overlap in the absorption spectrum, and the location of the Lb origin has been inferred from the substituent effects evident from the MCD spectrum (Steiner and Michl, 1978). 

Figure 19-22 compares absorption and fluorescence spectra of anthracene. Fluorescence comes at lower energy and is roughly the mirror image of absorption. To understand the mirror image relation, consider the energy levels in Figure 19-23. In the absorption spectrum, wavelength Xq corresponds to a transition from the ground vibrational level of Sq to the lowest vibrational level of Absorption...

In addition to a fluorescence perturbation, the Cd(II)-5d combination also uniquely yields aperturbation in the ultraviolet (UV) spectrum. A difference spectrum obtained by subtracting a fractional amount of an uncomplexed 5d spectrum from the perturbed spectrum is the mirror image of a fluorescence difference spectrum obtained by similar means. Moreover, excitation at 400 nm (where 1-4 are weakly absorbing but where moderate absorption is seen in the difference spectrum) gives rise to an emission spectrum with identical shape and Amax (456 nm) to that of the fluorescence difference spectrum. Thus, evidence points to the existence of two equilibrating ground state species as the physical basis for the chelatoselective emission. Bouas-Laurent has reported a related observation in methanol where a red-shifted CHEF was observed for a T1(I) 7r-complex.(14)... 

Many fluorescent dyes and proteins now available enable multiple detection channels and the ability to multiplex related assays. HCS assays typically use at least two channels one for a DNA stain and another for the fluorophore of interest. In general, the maximum number of channels utilized at one time ranges from two to five. Instrument hardware and driver software determine the number of channels and fluorophores to be acquired. Some factors to consider here include illumination source (arc lamp or laser), filter and mirror requirements, number of cameras or PMT detectors, camera sensitivity, and desired detection wavelength range. Other considerations for multiplexing include read time, resolution, and assay time (for live cell imaging). 

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