Fluorescence measurement, filter combination

Photomultipliers are appreciably more sensitive sensors than the eye in their response to line or continuum sources. Monochromators are fitted to the light beam in order to be able to operate as substance-speciflcally as possible [5]. Additional filter combinations (monochromatic and cut-off filters) are needed for the measurement of fluorescence. Appropriate instruments are not only suitable for the qualitative detection of separated substances (scanning absorption or fluorescence along the chromatogram) but also for characterization of the substance (recording of spectra in addition to hR and for quantitative determinations. 

Figure 6. Instrumental schematic for vacuum UV photofragmentation-laser induced fluorescence measurement of ammonia SHGC, second harmonic generation crystal SFMC, sum frequency mixing crystal BS, beam splitter BD, beam dump TP, turning prism CL, cylindrical lens R, reflector TD, trigger diode OSC, oscillator cell AMP, amplifier cell BE, beam expander G, grating OC, output coupler M, mirror BC, beam combiner L, lens A, aperture PD, photodiode SC, sample cell RC, reference cell FP, filter pack SAM.PMT, sample cell photomultiplier REF.PMT, reference cell photomultiplier PP, additional photomultiplier port EX, exhaust and CGI, calibration gas inlet to flow line. (Reproduced with permission from reference 15. Copyright 1990 Optical Society of America.)...

The chlorophyll sensor measures the red fluorescence radiation emitted by chlorophyll molecules (at 680 10 nm) when excited by blue radiation (at 435 50 nm). The fluorescence signal is optimized by using a single very intense pulse of blue radiation (—1-2 J per flash) repeated every 5-15 s, and two, specially selected filters in both blue and red channels to eliminate the detection of scattered radiation from any particulate material in the sample. The chlorophyll sensor optical system and filter combination are shown in Figure 3. 

Measurements of fluorescence lifetimes were carried out using the nanosecond fluorimeter and data analysis described by Kinosita et al. (1981). Fluorescence was excited at 435 nm from a hydrogen lamp (10 KHz). Emission wavelengths were set by interference filters and appropriate filter combinations at 684, 698 and 727 nm. The results were analysed assuming one or two decay components, hence monophasic (M) and biphasic (B) analyses. 

Color-order systems, such as the many MunseU collections available from Macbeth, have been described previously. Essential for visual color matching is a color-matching booth. A typical one, such as the Macbeth Spectrahte, may have available a filtered 7500 K incandescent source equivalent to north-sky daylight, 2300 K incandescent illumination as horizon sunlight, a cool-white fluorescent lamp at 4150 K, and an ultraviolet lamp. By using the various illuminants, singly or in combination, the effects of metamerism and fluorescence can readily be demonstrated and measured. Every user should be checked for color vision deficiencies. 

To clarify the mutual interactions between the gas bubbles and its surrounding liquid flow (mostly turbulent) in a bubbly flow, information of bubble s shape and motion is one of the key issues as well as the surrounding liquid velocity distribution. Tokuhiro et al. (1998, 1999) enhanced the PIV/LIF combination technique proposed by Philip et al. (1994) with supplementation of SIT to simultaneously measure the turbulent flow velocity distribution in liquid phase around the gas bubble(s) and the bubble s shape and motion in a downward flow in a vertical square channel. The typical experimental setup of the combination of PIV, LIF, and SIT is shown in Figure 14. The hybrid measurement system consists of two CCD cameras one for PIV/LIF (rear camera) and the other for SIT (front). The fluorescent particles are Rhodamine-B impregnated, nominally 1-10 pm in diameter with specific density of 1.02, and illuminated in a light sheet of approximately 1 mm thickness (Tokuhiro et al., 1998,1999). The fluorescence is recorded through a color filter (to cut reflections) by the rear camera. A shadow of the gas bubble is produced from infrared LEDs located behind the gas bubble. A square "window" set within the array of LEDs provides optical access for... 

The last system shown in Table 6.3 corresponds to a filter in combination with a method of chemical analysis such as x-ray fluorescence. It provides data on the chemical composition of the entire aerosol. The particles are collected on a filter usually over a period of hours. Concentrations measured by whole sample chemical analysis can be represented by the following expression ... 

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