How the spectrometer works
As we all know, spectral analysis is based on the constant movement of atoms and molecules in a substance. The internal movement of this substance can be reflected in the form of energy radiation and absorption outside. This form is electromagnetic radiation. The spectrum is electromagnetic radiation arranged in order of wavelength. Because the movement of atoms and molecules is diverse, the types of spectroscopy and spectral analysis instruments are also diverse. Generally, it can be divided into:
r ray 0.005 ~ 1.4
X-ray 0.1 ~ 100
Optical spectrum 100 to 300μm
Microwave spectrum 0.3mm ~ lm
The optical spectrum can be divided into:
Vacuum ultraviolet spectrum 100-200. Enter
Near ultraviolet spectrum 2000 to 3800
Visible spectrum 3500 to 7800
Near-infrared spectrum 7800 ~ 3μm
Far infrared spectrum 3 ~ 30μm
The so-called spectrum or spectrum analysis instruments generally refer to optical spectrum analysis instruments. From its appearance, it can be divided into line spectrum, band spectrum and continuous spectrum. The line spectrum is generated by the excitation of atoms or ions in the gas state. If it is generated by atoms, it is called atomic spectrum. If it is generated by ions, it is called ion spectrum. The band spectrum comes from the excited gas molecules. If the carbon electrode used in spectral analysis can be combined with nitrogen in the air at high temperature to generate cyanide (CN) molecules, when the cyanide molecules are excited in the arc, a band spectrum is generated, called the cyanide band. When the liquid or solid state of a substance is excited at a high temperature, a continuous spectrum is generated. Such as common incandescent lamps (tungsten filament lamps), red iron electrodes and so on. They emit continuous spectrometers. These spectra cannot be used for analysis.
According to the nature of electromagnetic radiation, the spectrum can be divided into atomic spectroscopy instruments and molecular spectroscopy instruments. According to the transmission of radiant energy, the spectrum can be divided into emission, absorption, luminescence (fluorescence spectrum) and Lehman spectrum. The essence of spectroscopic analysis that we are used to talking about here refers to "atomic emission spectrometry". Emission spectrum works in the spectral range of wavelengths of approximately 1600 to 8500.
According to the working principle of modern spectroscopic instruments, spectrometers can be divided into two categories: classic spectrometers and new spectrometers. Classical spectroscopic instruments are based on the principle of spatial dispersion; new spectroscopic instruments are based on the principle of modulation. Classical spectroscopy instruments are all slit spectroscopy instruments. Modulation spectroscopy instruments are non-spatial spectroscopy, which uses round holes to enter light.
According to the spectroscopic principle of dispersive components, spectroscopic instruments can be divided into: prism spectrometer, diffraction grating spectrometer and interference spectrometer. Optical Multi-channel Analyzer OMA (Optical Multi-channel Analyzer) is a new type of spectroscopic analysis instrument using photon detector (CCD) and computer control which has appeared in the past decade. Because OMA no longer uses photosensitive latex, it avoids and omits the darkroom processing and a series of cumbersome processing and measurement work, which has caused a fundamental change in traditional spectroscopy technology, greatly improved working conditions, and improved work efficiency; using OMA Analyze the spectrum. The measurement is accurate, rapid, convenient, and has high sensitivity, fast response time, and high spectral resolution. The measurement result can be immediately read from the display or output by the printer or plotter. It has been widely used in almost all spectrum measurement, analysis and research work, especially suitable for the detection of weak signals and transient signals.
The analysis process of the spectroscopic analysis instrument is to introduce the sample of the measured substance into the light source, and give external energy to evaporate the sample into gas atoms, and the outer electrons of the gas atoms are excited from the low energy state to the high energy state. Atoms in high-energy states are very unstable and have to transition to the ground or low-energy state, which produces radiation. Because the analyzed sample contains different atoms, it will produce different wavelengths of radiation. The spectrometer will split the generated radiation, and a regular spectral line arranged in order of wavelength will be obtained on the photosensitive plate. Identifying the existence of spectral lines of various characteristic wavelengths is the qualitative analysis of spectra. If it is further measured with a spectrum analyzer, it is a quantitative analysis of the spectrum.
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