Resolution of a grating

Resolution measures the ability to separate two closely spaced peaks. The greater the resolution, the smaller is the difference (AX.) between two wavelengths that can be distinguished from each other. The precise definition (which is beyond the scope of this discussion) means that the valley between the two peaks is about three-fourths of the height of the peaks when they are just barely resolved. The resolution of a grating is given by... 

Figure 3.1-8 The resolution of a grating spectrometer. D is the width of the diffracted beam and B the width of the grating.

After this discussion of the resolution of a grating spectrometer, we proceed to the question of the resolution obtained with a Michelson interferometer. For... 

From Eq. (5.7) we obtain the resolution of a grating spectrometer as limited by the slit width (see also Section 3.1) 3)... 

Resolution of a Grating. The resolving power of a grating is given by... 

Write the expression for resolution of a grating ruled to be most efficient in second order. To resolve a given pair of wavelengths, will you need more or fewer lines if the grating were ruled in first order ... 

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) ... 

In practice, the resolution of a grating monochromator system in the UV is usually assessed by measuring benzene vapor, which gives rise to a number of close but sharp absorption lines. Sealed quartz cells containing benzene vapor are commercially available for performing this assessment, which is normally done at several bandwidths, as shown in Figure 2.25. 

Figure 2.25 (a) Spectrum of benzene vapor, (b) Spectra of benzene vapor taken at two different bandwidths for testing resolution of a grating-based Instrument. (Courtesy of Starna Cells, Inc., Atascadero, CA, WWW. starnacel ls.com.)... 

Calculate the spectral resolution of a grating spectrometer with an entrance slit width of 10 p.m, focal lengths /i = /2 = 2 m of the mirrors Ml and M2, and a grating with 1800grooves/mm. What is the useful minimum slit width if the size of grating is 100 x 100 mm ... 

Figure 8 Comparison of the resolution of a FT-IR (Michelson) spectrometer to that of a grating spectrometer. The solid lines represent the resolution of a grating spectrometer with a bandpass of 10 nm and the resolution (in nm) for a FT-IR spectrometer operating at a nominal resolution of either 4 cm- or 16 cm- (because noise levels rapidly increase for narrower slitwidths, a 10 nm bandpass is typical of analytical rapid-scanning grating spectrometers). For example, a FT-IR spectrometer operating at 4 cm- resolution has an effective bandpass of 2.5 nm at 2500 nm, falling to less than 0.5 nm at 800 nm.

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