Application of Spectral Instrument and Technology

- Apr 27, 2018 -

The light is generated by the electrons that move inside the atom. The movement of electrons in the atoms of the various substances is different, so they emit light waves are also different. The study of the light emission and absorption of light from different substances has important theoretical and practical significance and has become a specialized discipline - spectroscopy. The direct spectrum of the emission of the object is called the emission spectrum. There are two types of emission spectra: continuous spectrum and bright line spectrum. The continuous distribution of spectra containing red shades of light from various colors is called continuous spectrum. The emission spectrum of hot solid, liquid and high pressure gas is continuous spectrum. Such as the light emitted by the filament, the light emitted by the hot molten steel forms a continuous spectrum.

The spectrum containing only some discrete lines is called the bright line. The bright lines in the bright line spectrum are called spectral lines, and the lines correspond to light of different wavelengths. The emission spectrum of the vapor of the thin gas or metal is the bright line spectrum. The bright line spectrum is emitted by the free state of the atom, so also called atomic spectrum. Observe the atomic spectrum of the gas, you can use the spectrometer, which is a relatively small closed glass tube, which is equipped with low-pressure gas, the tube has two electrodes at both ends. The two electrodes connected to the high-voltage power supply, the tube of thin gas glow discharge, resulting in a certain color of light.

Observe the atomic or liquid material of the atomic spectrum, you can put them into the flame or arc of the gas to burn, so that they gasification after the light, you can see from the spectroscope to their bright line spectrum.

Experiments show that the atoms are different, the emission of the bright line spectrum is also different, each element of the atoms have a certain bright line spectrum. Each atom can only emit light of certain wavelengths with its own characteristics, so the line of the bright line spectrum is called the characteristic line of the atom. The use of atomic characteristic lines can identify matter and study the structure of atoms.

Absorption spectra of high temperature objects emitted by white light (which contains all the wavelengths of continuous distribution of light) through the material, some wavelengths of light absorbed by the material after the spectrum, called the absorption spectrum. For example, let the white light emitted by the arc through the lower temperature of the sodium (in the alcohol lamp on the heart of some salt, salt decomposition will produce sodium), and then use the spectroscope to observe, you will see in the continuous spectrum There are two dark lines in the background, which is the absorption spectrum of the sodium atoms. It is worth noting that each of the dark lines in the absorption spectra of the various atoms corresponds to a bright line in the emission spectrum of the atoms. This indicates that the light absorbed by the cryogenic gas atoms is exactly the light that this atom emits at high temperatures. Thus, the spectral line in the absorption spectrum (dark line) is also the characteristic line of the atom, except that the characteristic spectrum usually seen in the absorption spectrum is less than that in the bright line spectrum.

Spectral analysis Because each atom has its own characteristic line, it can be based on the spectrum to identify the material and determine its chemical composition, this method is called spectral analysis. Do spectral analysis, you can use the emission spectrum, you can also use the absorption spectrum. The advantage of this method is very sensitive and rapid. A certain element in the material content of 10-10 grams, you can find it from the spectrum of its characteristic lines, which can check it out. Spectral analysis has a wide range of applications in science and technology:

In the inspection of semiconductor materials, silicon and germanium is not to achieve the requirements of high purity, it is necessary to use spectral analysis;

Historically, spectroscopic analysis has also helped to find many new elements, such as rubidium and cesium, which have been seen from the spectrum of characteristic lines that were previously unknown;

Spectral analysis is also useful for studying the chemical composition of celestial bodies. At the beginning of the nineteenth century, when studying the solar spectrum, it was found that there were many dark lines in its continuous spectrum. Initially do not know how these dark lines formed, and later people understand the absorption of the genesis, only to know that this is issued by the sun within the light through the relatively low temperature solar atmosphere generated when the absorption spectrum. Careful analysis of these dark lines, it is consistent with the characteristics of various atomic lines, people will know the sun's atmosphere contains hydrogen, helium, nitrogen, carbon, oxygen, iron, magnesium, silicon, calcium, sodium and other dozens of elements.

The color of the complex light is divided by the order of the wavelengths after the dispersion system, such as the sunlight, after the formation of the color spectrum according to the order of red orange, yellow, green and blue indigo. The structure of the spectrum, the mechanism, nature and its application in scientific research and production practice have accumulated a lot of knowledge and constitute a very important discipline ~ spectroscopy. Spectroscopy is widely used, and each atom has its own unique spectrum, as if people are "fingerprints" as different. They form a number of spectral lines according to certain laws. The nature of the atomic spectral line is closely related to the atomic structure and is an important basis for studying the atomic structure. Spectral analysis can be carried out using the principles and experimental methods of spectroscopy. Each element has its own unique spectral line, and it can be seen that the atomic spectrum generated by a substance is compared with the marker line of the known element Which elements are composed, with the spectrum not only qualitative analysis of the chemical composition of the material, but also to determine the amount of element content. Spectral analysis methods have a high sensitivity and accuracy. In the geological exploration using spectral analysis can be tested in the ore containing trace amounts of precious metals, rare elements or radioactive elements. With spectral analysis speed, greatly improving the work efficiency, but also can be used to study the spectral composition of the celestial bodies and calibration of the standard length of the original device.

A pattern arranged in order of wavelength (or frequency) after splitting through a dispersion system (such as a prism, grating). For example, the sun passes through the prism to form a continuous color spectrum of red, orange, yellow, green, blue, indigo, and purple order. Red to purple, corresponding to the wavelength from 7,700-3,900 angstroms, is visible to the human eye can see the part. Red outside the longer wavelength of infrared light, purple end of the wavelength is shorter than the UV light, can not be perceived by the naked eye, but can be recorded with the instrument.

Therefore, according to the wavelength region, the spectrum can be divided into infrared spectrum, visible spectrum and ultraviolet spectrum; according to the nature of the generated, can be divided into atomic spectrum, molecular spectrum; according to the different ways, can be divided into emission spectrum, absorption spectrum and Scattering spectrum; according to the spectral appearance of different morphology, can be divided into line spectrum, with spectral and continuous spectrum.

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