## Monochromators M250 series

Monochromator is a device that, thanks to setting the angle of the diffraction grating allows filtering from the wide spectrum of input light, the particular wavelength set by the user.

M250 monochromators are built in the Czernego-Turner configuration. The effective aperture of monochromators is f/5 and is defined by the focal length of the collimating mirrors f=250mm and the diameter of the diffraction grating D=50. Such an aperture allows for reduction of aberration while maintaining high energy of light falling on the grid. The width of slits of the monochromator can be adjusted in the range from 0 to 3mm and with the resolution of 0,01mm. The height of slits is 20mm and the overall size is 290 x 220 x 175.

The spectral range of the device depends on the diffraction grating used. M250 monochromators are offered in the following versions:

Linear dispersion of the monochromator P is determined as the ratio of the distance between adjecent grooves d and the focal length of mirror system f and it is expressed in [nm/mm]. Linear dispersion depends additionally on diffraction angle β and the diffraction order m.

Values of linear dispersion for the primary wavelengths is given in the table above. Long focal length of M250 monochromators allows for precise selection of the wavelength.

The accuracy of the instrument's setting depends on the diffraction grid used and ranges from 0.8 nm for a grid of 1200 lines / mm to 1 nm for a grid of 600 lines / mm.

M250 monochromators are equipped with a mechanical counter of the wavelength. Counter indications for monochromators with 1800 lines / mm grid correspond to a given wavelength. for monochromators with other grids, the counter display should be multiplied by a constant factor; 1.5 for a grid of 1200 lines / mm and 3 for a grid of 600 lines / mm.

It is possible to equip the monochromator with a stepper motor together with a controller, which allows controlling of the device by a computer.