The spectrum is electromagnetic radiation arranged in order of wavelength (or wave number, frequency). The rainbow of the sky, the aurora of nature, etc. are the spectrums observed in the early days, but they are only a small part of the visible spectrum of electromagnetic radiation. There are also a large number of spectra that cannot be directly seen and perceived by people, such as gamma rays, x-rays, ultraviolet rays, infrared rays, microwaves, and radio waves. These are also electromagnetic radiations, which differ only in frequency or wavelength.
Electromagnetic radiation is actually an energy (light quantum flow) that travels through space at great speed, with volatility and granularity.
In terms of volatility, the propagation of electromagnetic radiation in space has the properties of waves. Just like the propagation of sound waves and water waves, it can be described by parameters such as velocity, frequency, wavelength and amplitude, and does not use any medium for propagation, and is easy to pass. vacuum. The speed of all electromagnetic radiation in the vacuum is the same, usually expressed as the speed of light (c), the value of c is: 2.97972 * 10 3 m / sec.
In a certain medium, the relationship between them is
δ=V/C=1/λ
Where: V-------frequency, wave number per unit time; λ.........wavelength, which is the interval between two points of the same wave direction along the propagation direction of the wave; ............wavenumber, the number of wavelengths per unit length. C is the speed of light.
In terms of the granularity of electromagnetic radiation, each photon has its characteristic energy ε, and its relationship with wavelength or frequency can be expressed by the Planck formula:
ε=hv=h(c/λ) The wavelength is the interval between two points with the same phase in the adjacent phase.
Where: h is the Planck constant and its value is 6.626*10 -34 joules/second
2 , electromagnetic spectrum region
Electromagnetic radiation is arranged in a wavelength order called a magnetic spectrum. They are an objective reflection of the internal motion of matter, that is, the energy ε of a photon of any wavelength and the internal energy of a substance change △E=E 2 -E 1 =ε=hv=h(c/λ)
If the substance is known to transition from one state, E 2 to another state E 1 , the energy difference is ΔE=E 2 -E 1
The wavelength of the corresponding photon can be calculated according to the formula. The table below lists the various radiation areas, wavelength ranges, and the corresponding energy and transition types.
For the composition analysis, the near-ultraviolet and visible light regions are mainly applied.
Table 1 Electromagnetic spectrum region
Radiation area | Wavelength range | Transition type |
Gamma ray zone | 5-140 picami | Nuclear energy level transition |
X-ray zone | 0.01-10.0 nm | Inner electron energy transition |
Far ultraviolet region | 10-200 nm | Atoms and molecules |
Near ultraviolet region | 200-380 nm | Outer layer electronics |
Visible area | 380-780 nm | Energy level transition |
Near infrared region | 0.78-3 microns | Molecular vibration |
Mid-infrared region | 3-30 microns | Energy level transition |
Far infrared region | 30-300 microns | Molecular rotational energy level transition |
Microwave zone | 0.3 mm - 1 m | Electron spin and nuclear spin |
Radio frequency zone | 1-1000 meters | Energy level transition |
Note: 1 m = 10 3 mm = 10 6 microns = 10 9 nm = 10 12 picometers
3 , spectral analysis content
Spectral analysis is a type of analytical field that studies the chemical composition, structure, and state of existence based on the characteristic spectrum of a substance. It can be subdivided into various analytical methods such as atomic emission spectrometry, atomic absorption spectrometry, molecular emission spectroscopy, molecular absorption spectroscopy, X-ray fluorescence spectroscopy, infrared and Raman spectroscopy.
Atomic emission spectroscopy is a method for studying the chemical composition of a substance based on the characteristic radiant energy (different spectrum) emitted by the outer electron radiation transition of the sample material after it is excited by the gaseous atom (or ion). Often referred to as spectrochemical analysis, also referred to as spectral analysis. The photoelectric spectrum analysis method is an emission spectrum analysis measured by a photoelectric conversion device. In the field of photoelectric spectrum analysis, the application of computers has become widespread.
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