Spectroscopy double-beam optics

Fourier Transform Infrared Spectroscopy.—New Fourier transform (FT) spectrometers recently described in the literature include a double-beam optically compensated spectrometer suitable for weak i.r. absorptions (0.5—1%) and a... 

Spectrometers are instruments that provide information about the intensity of light absorbed or transmitted as a function of wavelength. Both single-beam and double-beam optical systems (see the schanatics in Chapter 2) are used in molecular absorption spectroscopy. Single-beam systems... 

In the laboratories of BASF (Badische Anilin- and Soda-Fabrik) at Ludwigshafen, the importance of infrared spectroscopy for industrial purposes was realized as early as the 1930 s. The first IR instrument with a modulated beam was built by Lehrer in 1937 and modified to a double beam instrument with optical compensation in 1942. Luft described the first non-dispersive infrared analyzer in 1943. He used the gas to be analyzed as absorber in a photo-acoustic detector cell. Thus, the instrument was sensitive only to this gas. He also provided a survey of early industrial applications of infrared spectroscopy (Luft, 1947). 

In the double-beam system, the source radiation is split into two beams of equal intensity. The two beams traverse two light paths identical in length a reference cell is put in one path and the sample cell in the other. The intensities of the two beams after passing through the cells are then compared. Variation in radiation intensity due to power fluctuations, radiation lost to the optical system (e.g., cell surfaces, mirrors, etc.), radiation absorbed by the solvent, and so on should be equal for both beams, correcting for these sources of error. A dispersive spectrometer used for absorption spectroscopy that has one or more exit slits and photoelectric detectors that ratio the intensity of two light beams as a function of wavelength is called a spectrophotometer. 

Figure 2.1 Schematic of the optical path of a double-beam infrared spectrometer with a grating monochromator. Reproduced from Brittain, E. F. H., George, W. O. and Wells, C. H. J., Introduction to Molecular Spectroscopy, Academic Press, London, Copsnight (1975), with permission from Elsevier.

Optical double resonance. Assumed. Level-crossing spectroscopy. Optical double resonance. Optical pumping. Assumed. Ion beam spectroscopy. ... 

UV-visible optical spectroscopy was employed in this work in order to study the adsorption spectra of composite PESA films containing organic chromophores. The measurements were performed using a double beam UV4 UNICAM spectrophotometer. 

Meth. MW MB IR MODR method of measurement used in the given reference corresponding to the preceding quoted values microwave spectroscopy molecular beam resonance experiment-electric or magnetic resonance infrared with lasers microwave optical double resonance... 

Meth. LC QB OS ED MW MB EPR DR method of measurement for the values in this line of the table level crossing spectroscopy quantum beat spectroscopy optical spectroscopy electric deflection method microwave spectroscopy molecular beam resonance experiment-electric or magnetic resonance electron paramagnetic resonance double resonance experiments (MODR, RF/DR)... 

The motivation of that effort is to improve spatial resolution, spectral resolution, measurement accuracy and sensitivity. Also of great interest is the implementation of single shot multiplex spectroscopy for turbulent combustion diagnostics. The CARS spectrometer consists in a portable, lightweight source assembly developed jointly with Quantel and in detection kits which can be adapted to various experimental problems. The source assembly comprises a frequency-doubled yag laser and a tunable dye laser space is provided on the optical table for various beam handling and combining optics ( 1 ). ... 

For second harmonic generation (SHG), the tensor is y(2)(—2co co, co) (useful for frequency doubling and parametric down-conversion) while for the linear electrooptic or Pockels71 effect the tensor is y(2)(— co co, 0) (useful for Q-switching of lasers, for phase or amplitude modulators, and for beam deflectors) for optical rectification the tensor is y 2>(0 00, —co) for frequency mixing the tensor is y(2)(— co3 oolr co2) (useful for frequency up-converters, optical parametric oscillators, and spectroscopy). 

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