Emission bandwidth

Figure B3.6.1 Rayleigh and Raman bands in fluorescent spectra, as seen in scans for solvent baseline and hen egg white lysozyme (EWL) solutions (solid lines). Circles represent the spectrum of EWL with baseline subtracted. Parameters EWL A2ao = 0.05 Xex = 280 nm excitation and emission bandwidths, 2.5 nm scan rate, 100 nm/min five scans accumulated. Spectra were measured using a Perkin Elmer LS50B fluorescence spectrometer.

Since protein emission spectra are generally rather broad, larger emission bandwidths can usually be tolerated. Only where it is important to resolve tyrosine fluorescence from tryptophan fluorescence and the Rayleigh scattering peak is it necessary to minimize the bandwidth. In cases where only low concentrations of material are available, it is necessary to strike a balance between resolution and light intensity in order to obtain the best possible signal-to-noise ratio. Settings of 2.5 to 10 nm are normal. 

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. 

In Eq. (3), 039 and 023 are the cross sections for stimulated emission and absorption. For narrow-line absorption and emission spectra, these two cross sections are equal. For broadband spectra with emission bandwidth greater than kT, the cross sections are connected by a generalized Einstein relation (6J. The final term in Eq. (3) accounts for possible excited-state absorption from the upper laser level to higher excited-states indicated by the dashed level in Fig. 1. If aesa > a32> absorption from level 3 dominates stimulated emission and laser action is not possible. 

All fluorescence measurements were performed with a Perkin-Elmer (USA) Model LS-55 spectrofluorimeter with 1.0 cm quartz cell. The excitation and emission bandwidths were set at 10 nm throughout the experiment. Stock thallium solution (lmg/mL) was prepared by dissolving purified metal thallium. Working standard solutions were freshly prepared by appropriate dilution with doubly distilled demineralized water. 3-(4 -chIorophenyl)-5- (2 -arsenoxyl phenylazo) rhodanine(4ClRAAP) (2 10 4 mol/L) was prepared by dissolving 0.0944 g of the reagent in 1000 mL absolute ethanol. Working solution was freshly prepared by appropriate dilution with doubly distilled demineralized water. 

Fig. 7. Wavelength dependence of the ODMR signal frequencies in the phosphorescence 0,0-band region for native E. coli Trp repressor protein ( ) and the single point mutants WI9F (A) and W99F ( ). Sample compositions and conditions of excitation are given in the legend for Fig. 4. The sample temperature is 1.2 K, the emission bandwidth is 1.5 nm, and all data are corrected for passage effects. [From M. R. Eftink, G. D. Ramsay, L. Bums, A. H. Maki, C. J. Mann, C. R. Matthews, and C. A. Ghiron, Biochemistry 32, 9189 (1993), with permission.]...

Figure 6.4 Width of an atomic absorption line (Zn 213.9 nm line), greatly exaggerated, compared with the emission bandwidth from a continuum source such as a deuterium lamp.

Since ead > da when Eda°° > 0> the emission bandwidth is expected to be smaller than the absorption bandwidth. The reorganizational energy appropriate to the thermally activated electron transfer process is Ar(g) not Ai.(e). 

It is perhaps the mode-locked operation of the color center laser that has been the most spectacular. Taking advantage of the broad emission bandwidth, the laser output can be transformed into a train of tunable picosecond and femtosecond duration pulses. The femtosecond color center laser was one of the first tunable subpicosecond pulse source, and it is still used as a source with reasonable average output power (hundreds of milliwatts) and fast repetition rates ( 100 MHz). Such short pulses are extremely useful for the investigation of ultrafast phenomena in semiconductor materials and the nonlinear characteristics of optical fibers. 

Narrowband EMI Interference whose emission bandwidth is less than the bandwidth of EMI measuring receiver or spectrum analyzer. 

Spectral narrowing of the emission and an increase of the laser output energy due to the presence of the nanoscatterers are predicted by the model in good qualitative agreement with experiment. In Figure 11 it is shown the calculated (a) and experimental (b) evolution of the emission bandwidth for different densities of scatterers. It is... 

Fig. 14.12 The effect of varying the emission bandwidth on the photoluminescence spectrum of europium (III) (in Naj o8Ko.5Eui,i4Si308 5 I.78H2O, = 393 nm). As the bandwidth increases...

The fluorescence spectra of the LB films were recorded on a Hitachi 850 fluorescence spectrophotometer (Japan) with the excitation bandwidth of 5 nm and the emission bandwidth of 5 nm. X-ray diffraction of the LB films was carried out on a Rigaku/rB diffractometer. UV-vis spectra were recorded on a Shimazu UV-240 (Japan) spectrophotometer. 

Figure 5.25 Source emission bandwidth compared with absorption bandwidth. Ideally, the emission peak bandwidth is contained within the absorbance peak bandwidth if not, poor resolution results. Monochromator bandwidth is also a critical consideration. 

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