Multi-wavelength recording

Having established that the multi-wavelength transmission techniques offer a number of advantages, the Uv-vis reflectance spectra from concentrated polystyrene lattices have been recorded using fiber optics reflection probes. Although some averaging of the individual particle properties can be expected, reliable calibration and estimation of the particle properties is possible, since discrimination to the desired particle properties is found as it will be shown below. 

Historically, photographic films and plates have been used at the exit plane of the monochromators to detect the spectral patterns from analytes. The main advantage of this approach is its inherent multi-wavelength detection ability. Because photographic films and plates are area detectors with fantastic spatial resolution, the entire spectrum from a sample may be recorded on a 30-cm plate, which ultimately results in simultaneous multi-elemental analysis. Unfortunately, the dynamic range of photographic emulsion is limited and the response function is typically nonlinear. Furthermore, the overall process is extremely time consuming and chemically intensive (need for a darkroom. 

Multielemental Analysis Atomic emission spectroscopy is ideally suited for multi-elemental analysis because all analytes in a sample are excited simultaneously. A scanning monochromator can be programmed to move rapidly to an analyte s desired wavelength, pausing to record its emission intensity before moving to the next analyte s wavelength. Proceeding in this fashion, it is possible to analyze three or four analytes per minute. 

In phase fluorometry, the phase (and modulation) data are recorded at a given wavelength and analyzed in terms of a multi-exponential decay (without a priori assumption of the shape of the decay). The fitting parameters are then used to calculate the fluorescence intensities at various times, 2 > 3 > The procedure is repeated for each observation wavelength X, X2, A3,... It is then easy to reconstruct the spectra at various times. 

The surface morphology, thickness and quality of the deposited carbon films are analyzed by scanning electron microscopy (SEM), by energy dispersive x-ray (EDx) and by Raman spectroscopy (RS). The Raman spectrum was recorded using an argon ion laser Raman microprobe. The exciting laser wavelength is 632.81 nm with a laser power equal to 1.75 mW. The instrument was operated in the multi-channel mode with the beam focused to a spot diameter of approximately 2 pm. 

Synchroton radiation has been employed as a spectral source for a study of the absorption of HCN and DCN in the wavelength range 80—120nm. A vacuum-u.v. spectrophotometer for absorptions in the region 105—200 nm has been described. Solid-, liquid-, and gas-phase samples could be analysed at temperatures from —200 to 100 °C and at pressures between 0 and 150 atmospheres. The absorption spectrum of tra j-di-imide in the vacuum-u.v. has been measured. First-derivative u.v. spectroscopy has been employed in the analysis of Watts nickel plating solutions for trace amounts of saccharin. Impurity levels of 0.1 p.p.m. have been recorded. A wavelength modulated derivative spectrophotometer with a multi-pass absorption cell has been developed for the automatic analysis of atmospheric pollutants. Traces of SOj, NO, and NO2 were detected with limits of 15, 13, and Sp.p.b., respectively. A double-beam single-detector absorption spectrometer has been constructed. Independence... 

In spectroscopy using continuous laser tuning it is very important to be able to monitor the change in wavelength. For this purpose, a stable multi-pass interferometer (Sect. 6.2.3) can be used, from which the fringes are recorded together with the spectrum [9.55]. 

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