Spectral analysis and types of spectra

Spectral analysis and types of spectra



Spectral analysis is a method of quantitative and qualitative determination of the composition of a substance. It is based on the study of absorption, emission, and luminescence spectra.





Spectral analysis and types of spectra

















Methods of spectral analysis

Spectral analysis is divided into severalindependent methods. Among them are: infrared and ultraviolet spectroscopy, atomic absorption, luminescence and fluorescence analysis, reflection and Raman spectroscopy, spectrophotometry, X-ray spectroscopy, and a number of other methods. Absorption spectroscopic analysis is based on the study of absorption spectra of electromagnetic radiation. Emission spectral analysis is performed on the emission spectra of atoms, molecules or ions excited by various methods.

Atomic-emission spectral analysis

Spectral analysis is often called onlyatomic emission spectral analysis, which is based on the study of the emission spectra of free atoms and ions in the gas phase. It is carried out in the wavelength region 150-800 nm. A sample of the test substance is injected into the radiation source, followed by evaporation and dissociation of molecules, as well as excitation of the ions formed. They emit radiation, which is fixed by the recording device of the spectral device.

Working with spectra

The spectra of the samples are compared with the spectra of knownelements that can be found in the corresponding tables of spectral lines. So the composition of the analyte is recognized. Quantitative analysis involves determining the concentration of a given element in the analyte. It is recognized by the magnitude of the signal, for example, in terms of the degree of blackening or optical density of the lines on the photographic plate, according to the intensity of the light flux on the photoelectric receiver.

Types of spectra

A continuous spectrum of radiation is given by substances,which are in a solid or liquid state, and also dense gases. In this spectrum there are no discontinuities, waves of all lengths are represented in it. Its character depends not only on the properties of individual atoms, but also on their interaction with each other. A linear emission spectrum is characteristic for substances in the gaseous state, with the atoms hardly interacting with each other. The fact is that isolated atoms of a single chemical element emit waves of a strictly defined wavelength. As the gas density increases, the spectral lines begin to expand. To observe this spectrum, use a glow discharge in the tube or vapor of matter in the flame. If white light is passed through the non-radiating gas, against the background of the continuous spectrum of the source, dark lines of the absorption spectrum appear. The gas most intensely absorbs the light of those wavelengths that it emits in the heated state.