Spectrometer angular dispersion

Low-energy CID spectra are measured using triple quadrupole, ion trap, ICR or hybrid instruments. For tandem mass spectrometers in space, the collision chamber is most often a quadrupole in the RF mode only, which allows one to focus the ions that are angularly dispersed by the collision. The pressure difference between the collision cell and the rest of the analyser is obtained through differential pumping. 

For a prism spectrometer with a symmetrically arranged prism with the refractive index n at an angle 7 (Fig, 3.1-9), the angular dispersion is given by... 

The linear dispersion of an echelle grating dl/dX) is the focal length of the spectrometer (/) multiplied by the angular dispersion ... 

Both the R and FWHM values of a crystal can be varied by making the surface of the crystal microcrystalline (mosaic), by abrasion, or through a similar process. The angular dispersion 69/dk of a crystal spectrometer is related to the d spacing of the analyzing crystal and the order n of the reflection, that is. 

Equation 2.31 exemplifies that the shot-noise dominated LOD for an absorbing atom concentration can be reduced only by an enhanced radiance of the lamp, an enlarged transmittance and geometrical conductance of the spectrometer, an increased angular dispersion of the dispersing optical component, and/or an increased measuring time. All these improvements, however, produce square-root effects only. 

The attainable spectral resolving power of a spectrometer is determined by its angular dispersion. When passing the dispersing element (prism or grating), a parallel beam composed of two monochromatic waves with wave-... 

The dispersion of the refractive index of alkali halides and of other materials at energies above ujq has been used to produce reasonable monochromatic radiation. In prism monochromators, a parallel beam of polychromatic radiation incident on a prism made from these materials is dispersed, with angular deviations depending on the dispersion uj2dn/duj of the refractive index with the photon energies. Before the advent of grating monochromators and Fourier transform spectrometers, the prism monochromators were widely used in optical spectroscopy and they are still used for specific experiments. 

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