If a classically ruled grating is employed, ghosts and stray light will increase as the square of the order. The main disadvantages of this approach are that the grating efficiency would not be as great as an optimized first order grating and order-sorting filters are typically inefficient. This slit is critical to the spectrometer’s performance and determines the amount of light (photon flux) that enters the optical bench and is a driving force when determining the spectral resolution. Wavelength selective filters may then be used to eliminate the unwanted radiation. A spectrometer is an imaging system which maps a plurality of monochromatic images of the entrance slit onto the detector plane. In this case, any first order light at 500 nm would be superimposed on top of the 250 nm light (and vice-versa).
However, if a dispersion of 0.77 nm/mm is necessary in the wavelength at 250 nm, this wavelength could be monitored at 500 nm in first order with the 1800 g/mm grating and obtain a second order dispersion of 0.75 nm/mm. Step 5: Calculate focal length of focus lens Once the width of the detector is know you can calculate the focal length of the focusing mirror/lens. Keeping in mind that kλ = constant for a given groove density, n, (Equation ( 9)), using second order with an 1800 g/mm grating to solve the last problem would not work because to find 600 nm in second order, it would be necessary to operate at 1200 nm in first order, when it has been shown in Table 6 that the maximum attainable first order wavelength is 867 nm. resolution you should aim for a wide detector (typically 1/1 or 25.8 mm). Therefore, if first order dispersion = 1.15 nm/mm with a 2400 g/mm grating, the same dispersion would be obtained with a 1200 g/mm grating in second order. Input your typical system use conditions and typical consumable costs associated with your current set-up to estimate many samples you can run in a year along. As dispersion varies with focal length (LB), groove density (n), and order (k) for a fixed LB at a given wavelength, the dispersion equation (Equation ( 5)) simplifies to: The following diagram displays the mass spectra of three simple gaseous compounds, carbon dioxide, propane and cyclopropane. In Example 2, the solution to the dispersion problem could be solved by using a 2400 g/mm grating in a 640 mm focal length system. It is defined as one twelfth of the rest mass of an unbound atom of carbon-12 in its nuclear and electronic ground state, and has a value of 1.660538782 (83)x10 -27 kg.
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