Brief introduction to spectroscopic techniques and their applications

Light waves are produced by electrons moving inside atoms. The movement of electrons in the atoms of various substances is different, so the light waves they emit are also different. The study of the luminescence and absorption of light by different substances has important theoretical and practical significance, and has become a specialized discipline—spectroscopy.
 
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Emission spectrum The spectrum directly produced by the light emitted by an object is called emission spectrum. There are two types of emission spectra: continuous and brightline.
 
A spectrum that is continuously distributed and contains various colors from red to violet is called a continuous spectrum. The emission spectra of hot solids, liquids, and high-pressure gases are continuous. For example, the light emitted by electric filaments and the light emitted by hot molten steel form a continuous spectrum.
 
A spectrum that contains only some discrete bright lines is called a bright-line spectrum. The bright lines in the bright-line spectrum are called spectral lines, and each spectral line corresponds to light of different wavelengths. The emission spectrum of a rarefied gas or metal vapor is a bright-line spectrum. The bright-line spectrum is emitted by atoms in the free state, so it is also called atomic spectrum. To observe the atomic spectrum of a gas, a spectral tube can be used, which is a closed glass tube with a relatively thin middle, containing low-pressure gas, and two electrodes at both ends of the tube. When the two electrodes are connected to a high-voltage power supply, a glow discharge occurs in the rarefied gas in the tube, producing light of a certain color.
 
To observe the atomic spectrum of solid or liquid substances, you can put them in the flame or arc of a gas lamp to burn them, make them vaporize and emit light, and you can see their bright-line spectrum from a spectroscope.
 
Experiments have shown that different atoms have different bright-line spectra, and the atoms of each element have a certain bright-line spectrum. Each atom can only emit light of certain wavelengths with its own characteristics. Therefore, the spectral lines of the bright-line spectrum are called the characteristic spectral lines of atoms. The characteristic spectrum of atoms can be used to identify substances and study the structure of atoms.