# MS750 series Monochromator-spectrograph, perfect imaging

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 While choosing a device configuration it is important to select properly the diffraction gratings. A right selection of the diffraction grating allows one to obtain the best combination of high energetic efficiency and spectral resolution. The basic grating parameters which determine their right choice you can find in the methodical material "Spectral Instrument. Basic Concepts and Characteristics." We propose a wide range of diffraction gratings to be used in the MS750 Series. Please, choose a necessary grating from the given below list, or consult our specialists.

#### Basic parameters for correct selection of diffraction gratings:

In the Table “Selection of diffraction gratings” groove density and blaze wavelength belong to a diffraction grating parameters. Other parameters characterize a spectral device together with a selected grating.

• Groove density. The diffraction grating has a periodic structure. Such parameters as resolving power and free spectral range are determined by the periodic structure properties of a diffraction grating. The period of grating is the distance through which grooves are repeated. The reciprocal value of a grating period is called the groove density and displays the number of grooves in 1 mm.

• Blaze wavelength. The reflectivity of a grating depends on the grooves geometry, because the direction to the center of the diffraction maximum is determined by the mirror reflection of the incident beam from the edge of a groove. In spite of rather flat profile of diffraction maximum a blaze wavelength that corresponds to the maximum efficiency of the grating has been adopted as a feature for convenience of calculation.
When selecting a grating it is useful to determine a blaze wavelength for a required grating on the spectral range of limited wavelengths WL1 and WL2. The blaze wavelength is determined by the ratio:
WLBlaze = 2 ∙ WL1 ∙ WL2 / (WL1 + WL2).

• Reciprocal linear dispersion. The light from a grating in the focal plane of a spectral instrument forms a spectrum. Linear dispersion is used for a spectrum characteristic, which is defined as a reciprocal value of the product of angular dispersion of a grating and focal length of a spectral instrument and shows the spectral range that falls on a single linear distance in a focal plane.

• The spectral resolution. Limiting resolution of a spectral instrument is equal to the minimum half-width of its instrument function. The instrument function is determined by finite sizes of entrance diaphragm, aberrations and also distortions caused by inaccuracy in manufacturing and adjustment of optical elements of instrument. In addition, instrument function, and thus spectral resolution are dependent on lighting method of entrance slit, used aperture and registration system parameters.

• Operating wavelength range. Energy efficiency range referred to the wavelength region in which grating reflection coefficient is not less than  0.405 of the maximum. In the first order this range is limited by the wavelengths: ⅔ ∙ WLBlaze and 2 ∙ WLBlaze.
Operating range usually corresponds to a grating energy efficiency. In some cases, for gratings with a high groove density and large blaze wavelength, the long-wave border of operating spectral range of instrument is limited by a maximal rotation angle of a grating which is defined by design of instrument.

#### Table for selection of diffraction gratings

 Model Line density,mm-1 Blaze wavelength, nm *Reciprocal linear dispersion, nm/mm Spectral resolution,nm Operating wavelengths range, nm Spectral range limited by the grating rotation angle, nm 75 - 0.11(wavelength 200 nm,120 order) 0.0024(wavelength 200 nm,120 order) - - 783600 3600 hol 0.33** 0.0064 185 - 450 500 782422 2400 225 0.52 0.01 185 - 450 750 782427 2400 270 0.51 0.01 185 - 540 750 782770 2400 400 0.47 0.009 270 - 750 750 781827 1800 270 0.7 0.014 185 - 540 1000 781840 1800 400 0.67 0.013 270 - 800 1000 781840 1800 500 0.63 0.012 335 - 1000 1000 781875 1800 750 0.51 0.01 500 - 1800 1000 781225 1200 250 1.08 0.021 185 - 500 1500 781228 1200 280 1.07 0.021 190 - 560 1500 781240 1200 400 1.05 0.021 270 - 800 1500 781250 1200 500 1.03 0.02 335 - 1000 1500 781260 1200 600 1 0.02 400 - 1200 1500 781275 1200 750 0.95 0.019 500 - 1500 1500 780623 600 230 2.19 0.043 185 - 460 3000 780630 600 300 2.18 0.043 200 - 600 3000 780640 600 400 2.17 0.043 270 - 800 3000 780650 600 500 2.16 0.042 335 - 1000 3000 780660 600 600 2.14 0.042 400 - 1200 3000 780675 600 750 2.11 0.042 500 - 1500 3000 7804008 400 800 3.23 0.06 535 - 1600 4500 7804012 400 1200 3.16 0.06 800 - 2400 4500 7804017 400 1700 3.03 0.06 1135 - 3400 4500 7804020 400 2000 2.94 0.06 1335 - 4000 4500 7804025 400 2500 2.75 0.06 1670 - 4500 4500 780330 300 300 4.39 0.09 200 - 600 6000 780335 300 350 4.39 0.09 235 - 700 6000 780350 300 500 4.38 0.09 335 - 1000 6000 780360 300 600 4.37 0.09 400 - 1200 6000 780370 300 700 4.35 0.09 470 - 1400 6000 7803010 300 1000 4.31 0.08 670 - 2000 6000 7803015 300 1500 4.23 0.08 1000 - 3000 6000 7803020 300 2000 4.11 0.08 1335 - 4000 6000 7803030 300 3000 3.8 0.08 2000 - 6000 6000 7803035 300 3500 3.59 0.08 2330 - 7000 6000 780235 200 350 6.6 0.13 235 - 700 9000 780240 200 400 6.6 0.13 270 - 800 9000 780250 200 500 6.6 0.13 335 - 1000 9000 780270 200 700 6.6 0.13 470 - 1400 9000 7802015 200 1500 6.5 0.13 1000 - 3000 9000 7802020 200 2000 6.4 0.13 1335 - 4000 9000 7802025 200 2500 6.3 0.13 1670 - 5000 9000 7802030 200 3000 6.2 0.12 2000 - 6000 9000 781547 150 475 8.8 0.17 320 - 950 12000 781570 150 700 8.8 0.17 470 - 1400 12000 7815030 150 3000 8.5 0.17 2000 - 6000 12000 7815045 150 4500 8.1 0.16 3000 - 9000 12000 780165 100 650 13.2 0.26 435 - 1300 18000 780170 100 700 13.2 0.26 470 - 1400 18000 7801010 100 1000 13.2 0.26 670 - 2000 18000 7801020 100 2000 13.1 0.26 1335 - 4000 18000 7801025 100 2500 13 0.26 1670 - 5000 18000 7801030 100 3000 12.9 0.26 2000 - 6000 18000 7801042 100 4200 12.7 0.25 2800 - 8400 18000 7801048 100 4800 12.6 0.25 3230 - 9600 18000 7801055 100 5500 12.5 0.25 3670 - 11000 18000 7801062 100 6200 12.3 0.24 4130 - 12400 18000 7801072 100 7200 12 0.24 4800 - 14400 18000 7801088 100 8750 11.5 0.23 5830 - 17500 18000 7801097 100 9700 11.1 0.22 6470 - 18000 18000 7801103 100 10300 10.9 0.21 6870 - 18000 18000 7875070 75 7000 16.7 0.33 4670 - 14000 24000 7875095 75 9500 16 0.32 6330 - 19000 24000 7850010 50 1000 26.4 0.52 670 - 2000 36000 7850038 50 3800 26.2 0.52 2530 - 7600 36000 7850063 50 6300 25.8 0.51 4200 - 12600 36000 7850070 50 7000 25.7 0.51 4670 - 14000 36000 7850083 50 8300 25.5 0.5 5530 - 16600 36000 7850124 50 12400 24.6 0.48 8240 - 24820 36000 7850169 50 16900 23.2 0.46 11270 - 33800 36000 7850200 50 20000 22 0.43 13330 - 36000 36000 7837028 37.5 2800 35.1 0.69 18700 - 5600 48000 7837056 37.5 5600 34.8 0.69 3735 - 11200 48000 7837093 37.5 9300 34.3 0.68 6200 - 18600 48000 7837156 37.5 15600 33 0.65 10400 - 31200 48000 7824116 24 11600 54 1.1 7730 - 23200 75000 7824144 24 14400 53.6 1.1 9600 - 28800 75000 7824173 24 17300 53.1 1.1 11530 - 34600 75000 7824243 24 24300 51.6 1 16200 - 48600 75000 7824285 24 28500 50.5 1 19000 - 57000 75000 7824325 24 32500 49.2 1 21670 - 65000 75000

* at the blaze wavelength

** at the wavelength 255 nm

For blaze wavelength 2000 nm and shorter the data measured by multielement detectors with entrance slit 15 microns.

For the wavelength more than 2000 nm the data obtained by calculation with the entrance slit 15 microns.