Dual-beam system

Optically aligned dual beam systems (Fig. 12.3) were then developed, to enable simultaneous acquisition of the spectrum from the reference and the sample. They record the intensity difference with and without passage of the beam through the sample. 

Fig. 77. Flame atomic absorption spectrometer. A. Single beam and B dual-beam system, (a) hollow cathode lamp (b) flame (c) monochromator (d) rotating mirror ...

Figure 2 Transient curve of thermai iens signal (A) singlebeam system using CW iaser (B) duai-beam system using CW exciting laser (C) dual-beam system using pulsed exciting laser.

Figure 28.2 Selection of commercially available TDLAS systems. Clockwise, from top to bottom universal dual-beam system with internal calibration cell, based on visible-near-IR laser diodes (LTG-LaserTech Inc) multispecies gas monitor, based on mid-IR QCLs (Cascade Technologies) miniature single-gas sensor, based on visible-near-IR laser diodes (Physical Sciences Inc.) single-/multi-gas system, based on mid-IR lead-salt lasers (Campbell Scientific Inc.) hand-held remote gas sensor, based on near-IR laser diodes (Physical Sciences Inc.)...

Figure 30. Flame atomic absorption spectrometer A) Single beam B) Dual-beam system...

A primary beam mass filter may be used to insure the purity of the beam reaching the sample. The Cameca IMS instruments with a dual beam system of a duoplasmatron and cesium source use a primary beam magnet as the beams exit the source area to mass separate the ion beam. A mass gate or filter would be used to select ions of different masses traveling at different velocities in the column of a thermal effusive ion source (example and Cgo in a Cgo source) [16]. A mass... 

Characteristics of the scattered light produced by a spherical particle, exposed to two plane waves, have been discussed by several investigators e.g., Hong Jones, and Pendleton . In a recent study, Naqwi Durst have generalized the previous formulations, so that, polarization of the individual beams can be specified independently, and the cases of arbitrarily oriented circular and rectangular apertures may be considered. Such a formulation is necessary for evaluating innovative applications of the dual-beam system. 

J. Johansson, M. Cauchi, M. Sundgren, Mnltiple fibre-optic dual-beam UVA is system with application to dissolution testing, J. Pharm. Biomed. Anal., 29, 469 76 (2002). 

The laser hres at f = 0 and causes an increase in absorbance in the sample as a consequence the intensity of light reaching the detector decreases. While laser photolysis systems are normally single-beam spectrometers, in fact they behave as dual-beam instruments. The reference beam is separated from the sample beam in time, rather than space. Thus, the reference signal is acquired before laser excitation and leads to Iq. The absorbance at time t in Figure 18.3 is given by Eq. 1 ... 

The key specifications of EL3 are shown in Table I. EL3 combines a high current variable shaped beam column with a dual deflection system (42). Maximum beam size is 4 jam x 4 jam and shapes smaller than this are available in 0.1 m increments. Spot edge definition is better than 0.2 jam. A highly accurate but relatively slow magnetic deflection coil deflects the beam in a raster sequence to the center of an array of 75 jim subfields. The variable... 

Figure 25-20 Photodiode array ultraviolet detector for HPLC. (a) Dual-beam optical system uses grating polychromator, one diode array for the sample spectrum, and another diode array for the reference spectrum. Photodiode arrays are described in Section 20-3. (fc>) Reversed-phase chromatography (using C18-silica) of sample containing 0.2 ng of anthracene, with detection at 250 nm. Full-scale absorbance is 0.001. (c) Spectrum of anthracene recorded as it emerged from the column. [Courtesy Perkln-Elmer Corp.. Norwalk. Cl]...

Absorption spectra of 2-nitroanisole in supercritical C02, N20, Freon-13, ammonia and C02-methanol mixtures were obtained on a Cary model 1605 spectrophotometer operated in the dual beam mode. The gases used as supercritical solvents were of the highest purity available from the supplier (Matheson) and were further filtered prior to use. The mixed solvent system of C02-methanol was obtained from Scott Speciality Gases (15.4 wt% methanol), and other mixtures were made in the laboratory. Spectra of 2-nitroanisole in n-pentane, methanol, tetrahydrofuran and acetonitrile (Burdick A Jackson) were obtained using quartz cells with a 1-cm light path and with a pure solvent blank in the reference beam. Vapor phase and supercritical fluid spectra were obtained using an air reference. 

The current status of prediction and modelling in the area of fuel spray combustion requires, among other parameters, the measurement of droplet or solid particle size distribution and the relative velocity between the fuel and the surrounding gas. Many optical techniques, based on laser light scattering, have been investigated to this purpose (Refs.1,2,2,]+,, 6 and j), but the only system able to simultaneously determine the size and the velocity is the dual-beam laser Doppler velocimeter shown in Figure 1. 

A Dual-Beam Photodiode Array Spectrometer System for Liquid Chromatographic Separation Methods Development... 

A multiwavelength, dual beam optical system with 256 detectors operating in a free spectral range of 200 to 800 nm has been designed and implemented for use with a liquid chromatograph. 

THIS SYSTEM IS COMPOSED OF XXX SUBPROGRAMS WHICH ACQUIRE DATA FROM A DUAL BEAM MULTIPLE WAVELENGTH DETECTOR IN A CONFIGURATION FOR USE WITH A HIGH PRESSURE LIQUID CHROMATOGRAPH. 

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