Spectrografie

Spectrografie, known in English as spectrography, is the scientific technique of analyzing light by dispersing it into its constituent wavelengths with a spectrograph and recording the resulting spectrum. The spectrum plots light intensity as a function of wavelength and can reveal the properties of the light source or the material that emitted, absorbed, or scattered the light. The information gained includes elemental composition, physical conditions such as temperature, density, and motion, and chemical or physical processes at work.

The basic setup involves collecting light, often through a slit, and passing it through a dispersive element such as a prism or diffraction grating. The dispersed light is then imaged onto a detector, which may be a photographic plate in older instruments or modern detectors like CCDs and photomultiplier arrays. Calibration steps include wavelength calibration using known emission lines and intensity calibration to convert detector response into absolute or relative intensity.

Spectrography encompasses several modes, including emission spectroscopy (analyzing light emitted by a sample), absorption spectroscopy (measuring light attenuation by a sample), and fluorescence spectroscopy. It is closely related to spectral imaging, where spatially resolved spectra are recorded for each pixel or voxel. Raman spectroscopy and related techniques are sometimes integrated with spectrographic methods.

Applications are broad: astronomy uses high-resolution spectrographs to determine chemical composition, temperature, and redshift of celestial objects; chemistry and materials science identify substances and characterize processes; environmental monitoring, forensic science, and art conservation also rely on spectrography for precise spectral information.