emissiemonochromator

An emission monochromator is an optical instrument used to isolate a narrow band of wavelengths from a broader emission spectrum. In spectroscopy, it is placed in the light path after the sample or light source to select a specific emission line for detection. The device relies on a dispersive element, typically a diffraction grating or a prism, to separate wavelengths spatially. An entrance slit defines the initial width, and after dispersion an exit slit selects the desired wavelength band, which is then focused onto a photodetector or detector array. In emission-mode operation, the sample is excited (by flame, arc, lamp, or other means) and the emitted light is analyzed.

Grating monochromators are common in UV–visible spectrometers and spectrofluorometers; they offer higher dispersion and wider spectral ranges. Prism monochromators provide smooth variation but lower spectral resolution. Double monochromators use two dispersive stages to suppress stray light and improve spectral purity.

Key performance parameters include spectral range, resolution (often expressed as the full width at half maximum of the transmitted band), and bandwidth determined by slit widths. Resolution is influenced by groove density in gratings, optical quality, and alignment. Stray light, blaze wavelength, and order overlap are important considerations, especially in emission measurements with weak signals.

Applications span atomic emission spectroscopy, flame photometry, plasma diagnostics, and fluorescence spectroscopy, where a precise emission wavelength improves signal-to-noise and allows quantitative analysis. In many instruments, an emission monochromator is paired with an excitation monochromator to separately tune excitation and emission pathways, ensuring selective detection of the target emission band.