Fluorescence optical train

Fig. 22 Optical trains of the commercially available scanners. (A) absorption, (B) fluorescence quenching and true fluorescence.

However, the optical train illustrated in Figure 22B allows the determination of fluorescence quenching. The interfering effect described above now becomes the major effect and determines the result obtained. For this purpose the deuterium lamp is replaced by a mercury vapor lamp, whose short-wavelength emission line (2 = 254 nm) excites the luminescence indicator in the layer. Since the radiation intensity is now much greater than was the case for the deuterium lamp, the fluorescence emitted by the indicator is also much more intense and is, thus, readily measured. 

The optical train employed for photometric determinations of fluorescence depends on the problem involved. A spectral resolution of the emitted fluorescence is not necessary for quantitative determinations. The optical train sketched in Figure 22B can, therefore, be employed. If the fluorescence spectrum is to be determined the fluorescent light has to be analyzed into its component parts before reaching the detector (Fig. 28). A mercury or xenon lamp is used for excitation in such cases. 

When recording excitation and fluorescence spectra it must be ensured that monochromatic light falls on the detector This can best be verified in instruments built up on the kit principle or in those equipped with two monochromators (spectrofluonmeters) The majority of scanners commercially available at the moment do not allow of such an optical train, which was realized in the KM3 chromatogram spectrometer (Zeiss) So such units are not able to generate direct absorption or fluorescence spectra for the charactenzation of fluorescent components... 

Evaluation of chromatograms la 133ff Evaluation, peak area or height la 31,33,40 -, optical trains la 30, 39 Evipan la 339,343 Excitation to fluorescence la 10,12,20,37 Explosion resulting from reagent residues la 82,253,261,315,365 Explosives lb 49,244,407-409 Exposure to vapors la 86... 

The optical train employed for photometric determinations of fluorescence de-... 

Figure 25.2. Side view of a laser microscope, illustrating the optical path taken by the laser hght dark arrow) once it has entered the epi-flluminator port. For a description of how the laser is coupled to the epi-illumination port, see Figure 25.3. In this example, the laser hght is reflected into the preparation using a conventional GFP fluorescence filter set, fi om which the exciter filter has been removed. The rest of the optical train includes elements needed for DlC/Nomarski optics, and the coupling of a video camera. As in Figure 25.3, the microscope would be securely braced and mounted to a vibration-damping optical table.

Fig. 18. Schematic of apparatus used to measure fluorescence kinetics with a streak camera. The Nd glass laser emits a train of one hundred 1.06 pm pulses separated by 6 ns. A single pulse in the earlier portion of the train is selected by a Pockels cell and crossed polarizers (Pi and P2). The high voltage pulse ( 5 ns) at the Pockels cell is supplied by a laser triggered spark gap and a charged line. The single pulse ( 8 ps, 109 W) can be amplified. The second harmonic is generated from a phase matched KDP crystal. Beam splitters provide two side beams beam (1) triggers the streak camera beam (2) arriving at the streak camera at an earlier time acts as a calibrating pulse. The main 0.53 pm beam excites the sample for fluorescence measurement. The fluorescence collected with f/1.25 optics is focused into the 30 pm slit of the streak camera. The streak produced at the phosphorescent screen is recorded by an optical multichannel analyzer. (After ref. 67.)...

A second detection scheme for observation of periodic excitation resonances is shown in Fig. 1b. The fluorescence radiation of the atoms which are optically excited by the pulse train, is monitored as a function of the pulse rate. At resonant coherent excitation of the atomic sample the incoming light is less absorbed and reduced fluorescence radiation is observed. In this case a cheap Ga(Al)As injection laser has been applied which is directly modulated and supplied with electrical pulses from a comb generator. The laser generates optical pulses of about Uo ps duration at a pulse rate of 1 GHz. 

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