Prism and Grating

prisms are quite useful in A AS as the majority of resonance lines lie in the UV region. However, glass prisms cannot be used in AA instruments because they do not pass ultraviolet radiation. For example, borosilicate glass is transparent from 310 to 2500 nm, while quartz is transparent from 170 to 2500 nm. 

The reciprocal linear dispersion for a grating is nearly constant over the entire wavelength region and it is dependent on the number of grooves per unit width, spectral order, and the focal length of the collimator. The resolution of a grating is a function of spectral order (m) and the total number of grooves N)  

The effective aperture width of a grating is the width of an individual groove (d) multiplied by the total number of grooves (N) and by cos r (r is the angle of reflection)  

For example, a grating ruled with 2000 grooves nm and 50 mm in width has a resolution in the first order of 100000. At the sodium wavelength of 589 nm, the smallest wavelength interval resolved will be A A = 589/100000 nm = 0.006 nm. 

AAS measurements are almost exclusively carried out in the first order, and a good grating has 2000 to 3000 grooves mm. The reciprocal linear dispersion of 1 nm mm or less can easily be obtained with the usual focal lengths employed. Comparable reciprocal linear dispersions are achieved with a conventional prism monochromator only in the far UV region, while in the near UV and visible regions grating monochromators are superior. 

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Axial elongation of the PSF may also result from the pulse tilt acquired after their passing through prisms and gratings, for example, in pulse compressors used in the standard chirped pidse ampHfication (CPA) scheme [41]. The influence of spherical aberrations on the PSF is discussed in Sect. 3.1.2. 

Both prism and grating monochromators and spectrographs have been used extensively for measuring Raman spectra. While monochromators are still the mainstay of Raman instrumentation, FT-Raman has made considerable advancement in recent years and is now considered to be competitive with monochromators. Both monochromators and FT-Raman will be discussed in detail. 

Prisms and Gratings. For a prism of refractive index n and refracting angle a, there is an angle of incidence 0 for which the deviation angle S is a minimum this can be used, for example, to determine the refractive index n of a liquid placed inside the hollowed prism (Fig. 2.19). 

We next discuss how to wavelength-select visible radiation. There have been two traditional kinds of optical elements prisms and gratings (Fig. 2.20). In particular, the Bunsen103 prism is a 60° prism, made of fused silica (normal glass absorbs too much light below 350 nm) a single natural quartz crystal is... 

Infrared Spectrometers. Infrared spectroscopy is one of the most powerful tools for quantitative and qualitative identification of molecules, and this led to the early development of prism and grating spectrophotometers. Typically, these instruments cover the region from 400 to 4000 cm, give a resolution of 1 to 4 cm, and require calibration with polystyrene films or with standard gases such as H2O, CO2, CH4, or This al-... 

Prisms and Gratings. Prisms and diffraction gratings are also widely used as monochromators. A prism separates... 

We often call the UV/visible and IR regions of the spectrum the optical region. Even though the optic nerve is responsive only to visible radiation, the other regions are included because the lenses, mirrors, prisms, and gratings used are similar and function in a comparable manner. Spectroscopy in the UV/visible and IR regions is, therefore, often called optical spectroscopy. 

The sensitivity of angular modulation-based SPR sensors to bulk refractive index (herein denoted as (Se)p 5 and (Se)g,ating for SPR sensors using prism and grating couplers, respectively) can be derived from Eqs. 12 and 13, and the equation for Stief/Sn obtained using the perturbation theory (Eq. 58... 

A monochromator consists of a dispersion element, an entrance slit and an exit slit, plus lenses and mirrors for coUimating and focusing the beam of radiation. The function of the dispersion element is to spread out in space, or disperse, the radiation faffing on it according to wavelength. The two most common types of dispersion elements are prisms and gratings. You are probably already familiar with the abUity of a prism to disperse white fight into a rainbow of its component colors. 

Emission spectra were first utilized in analytical chemistry as they were simpler to detect than absorption spectra. Flames, arcs, and sparks are all classical radiation sources. Lundegardh first applied a pneumatic nebulizer and an air-acetylene flame. The development of prism and grating instruments was parallel. Photography was employed to detect the spectral lines. The first commercial flame photometers came on the market in 1937. 

With a combination of prisms and gratings (Fig. 6.31) not only the quadratic but also the cubic term in the phase dispersion... 

On the other hand, those characteristics of the laser that are important for its applications in spectroscopy are treated in more detail. Examples are the frequency spectmm of different types of lasers, their linewidths, amplitude and frequency stability, tunability, and tuning ranges. The optical components such as mirrors, prisms, and gratings, and the experimental equipment of spectroscopy, for example, monochromators, interferometers, photon detectors, etc., are discussed extensively because detailed knowledge of modem spectroscopic equipment may be cmcial for the successfiil performance of an experiment. 

Dispersive oscillator A tunable laser oscillator that incorporates dispersion elements such as prisms and gratings. 

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