Luminescence bandwidth

The commercialization of inexpensive robust LED and laser diode sources down to the uv region (370 nm) and cheaper fast electronics has boosted the application of luminescence lifetime-based sensors, using both the pump-and-probe and phase-sensitive techniques. The latter has found wider application in marketed optosensors since cheaper and more simple acquisition and data processing electronics are required due to the limited bandwidth of the sinusoidal tone(s) used for the luminophore excitation. Advantages of luminescence lifetime sensing also include the linearity of the Stem-Volmer plot, regardless the static or dynamic nature of the quenching mechanism (equation 10) ... 

The luminescence emission spectrum of a specimen is a plot of luminescence intensity, measured in relative numbers of quanta per unit frequency interval, against frequency. When the luminescence monochromator is scanned at constant slit width and constant amplifier sensitivity, the curve obtained is the apparent emission spectrum. To determine the true spectrum the apparent curve has to be corrected for changes of the sensitivity of the photomultiplier, the bandwidth of the monochromator, and the transmission of the monochromator with fre-... 

Also, using dyes as laser media or passive mode-locked compounds requires numerous special parameters, the most important of which arc file band position and bandwidth of absorption and fluorescence, the luminescence quantum efficiency, the Stokes shift the possibility of photoisomcrization, chemical stability, and photostability. Applications of PMDs in otliei technical or scientific areas have additional special requirements. 

Broad band laser oscillation from Coumarin 153 doped ORMOSIL gels was easily obtained in the free-running laser cavity. The laser emission and the luminescence spectrum both peak at nearly the same wavelength as shown in Figure 4. The laser emission peak was at 526 nm with an oscillation bandwidth of approximately 20 nm FWHM. (For comparison, the reported total oscillation bandwidth in ethanol pumped at 308 nm is 75 nm.) The fluorescence spectrum has a broad peak at about 530 nm with a bandwidth (FWHM) of about 80 nm. 

The laser emission peak from R6G doped ORMOSIL gels occurred at 571 nm with a bandwidth of 4 nm. The laser emisison band is narrower than the FWHM fluorescence band. The doped ORMOSIL sample exhibited a luminescence peak at 565 nm with a bandwidth of 55 nm (FWHM) In contrast to the C153 gel, the solid state rhodamine doped sample did not oscillate over the FWHM range of die fluorescence emission spectrum. The R6G samples exhibited detectable oscillation over a total range of about 38 nm (559 to 587 nm). 

Scattered light collected by the FI.5 lens (f = 30 cm) is relayed to the photomultiplier tube via 1 mm slits, a 1 nm bandwidth interference filter and a polarization filter, to reduce background from flame luminescence. The PDP-11/34 computer instructs the A/D convertor to make a conversion every 100 vsec. The resulting digital data are stored sequentially in core memory. The memory is saturated at 16,000 temperature measurements, at which time the data are transferred to a hard disk memory. The data in this transfer constitute one time... 

The luminescent properties of tyrosine and tryptophan are affected by their microenvironments. Depending upon the location within the polypeptide structure and the neighboring charges, several classes of residues have been distinguished in native proteins (Cogwill 1968 Burstein et al. 1973). Each class exhibits mainly a distinct spectral emission maximum with a specific spectral bandwidth. Nevertheless, upon denaturation, the protein unfolds, and, as was first reported by Teale (1960), for most proteins, the quantum yields of tryptophan residues tend to become uniform. 

An ultrabroadband infrared laser oscillation has been obtained at 300 K with F2+ colour centres in LiF [25]. Its wavelength range, 850-1040 nm, is almost comparable to the bandwidth of the F2+ luminescence spectrum. Ultrabroad band laser oscillation is of interest in laser spectroscopy and photochemistry. 

Figure 11.13 The PL spectra from CN-PPP and CN-PPP doped with 5 wt.% of the indicated Eu complexes. All of the films had the same thickness and absorbed approximately the same amount of light, so the emission spectra can be compared to each other to determine relative quantum yields [50]. (Reproduced with permission from M.D. McGehee et al., Narrow bandwidth luminescence from blends with energy transfer from semiconducting conjugated polymers to europium complexes, Advanced Materials, 1999, 11, 1349-1354. Wiley-VCH Verlag GmbH Co. KGaA.)...

McGehee, M.D., Bergstedt, T., Zhang, C., et al. (1999) Narrow bandwidth luminescence from blends with energy transfer from semiconducting conjugated polymers to europium complexes. Advanced Materials, 11, 1349-1354. 

Fig.11.2 Optical spectra of various optical probes, (a) Photo-luminescence spectra of Q-dots (from the work by Michalet et al. [2]), (b) scattering spectra of gold nanoparticles with different aspect ratio (from the work by Jain et al. [3]), and (c) fluorescence spectrum of FITC (black line) and SERS spectrum (red line) of benzene thiol with 514.5 nm photo-excitation (from the work by Jun et al. [4]). Raman band has much narrower bandwidth than the others...

The phosphorescence spectrum ofthe primary electron donor is illustrated for Rb. sphaeroides in Fig. 15 (B). Phosphorescence from the Rb. sphaeroides reaction center complex with the quinones removed was detected at 20 Kon the long-wavelength side ofthe fluorescence and displayed an emission band with a maximum at 1318 nm (or 7590 cm ) and a half bandwidth of240 cm. The ratio of the integrated intensities of this 1318-nm luminescence to that ofthe fluorescence was, as expected, quite small, only... 

The advent of fast response detectors with IR sensitivity and high bandwidth, high gain amplifiers has provided the capability of detecting the extremely weak luminescence at 1269 nm [32-37], This has allowed the accurate determination of lifetimes directly from the exponential decay of the IR emission, quenching rate constants by appropriate use of Eq. (15). 

Selecting a Secondary Filter and Measuring Emission. After penetrating the aperture, the emitted luminescence passes through a secondary filter or fluorescence grating that eliminates any scattered radiation. The bandwidths of the primary and secondary fitters should not overlap. For example, if a 7-60 primary filter were used, then the secondary filter chosen should not transmit below about 400 nm a good choice would be the so-called 2A secondary filter shown in Figure 9.5B. 

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