What Is Continuous Spectrum?
Continuous spectrum refers to a spectrum where the intensity of light (radiation) is continuously distributed with frequency. According to quantum theory, atoms and molecules can be in a series of discrete states. The transition between the two states produces a spectral line. Each spectral line system tends to a short-wave limit, and a wavelength shorter than this limit results in a continuous region of the spectrum (see Atomic Spectrum). This limit is called the line limit. From the position of the line restraint, the intensity of the continuous region decreases rapidly. This continuous region is a continuous spectrum. [1]
- Continuous spectrum refers to
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- In recent years, the continuous spectrum analysis technology has been increasingly applied in the field of water quality monitoring instrument technology. Based on the principle of continuous spectrum analysis, it can not only detect multiple water quality parameters (that is, the measured substance in water samples), but also because continuous spectrum carries The important information of the measured substance can be expanded to signal processing in a wide spectral range to effectively eliminate the error of the detection instrument system, reduce the background spectral interference (such as turbidity) and noise interference, thereby greatly improving the accuracy of online water quality detection [3]
- The continuous spectrum of hot solids and liquids and high-temperature and high-pressure gases cannot be understood simply by the theory of the Bohr atomic level transition. Unlike thin gas being ionized, the distribution of electrons outside the nuclei of hot solids and liquids and high-temperature and high-pressure gas is more complex, and the atomic distribution is more dense. Due to the interaction between atoms, slight changes in atomic orbital energy will be caused. Bohr's theory no longer applies. From the classical theory, it can be explained that the electrons around the atom are ionized, and when the high-speed moving electrons collide with the ions, a large negative acceleration will occur, and a sharply changing electromagnetic field, that is, electromagnetic radiation, will be generated around them. Because the collision process and conditions and the energy change of each collision are random, continuous electromagnetic radiation with different wavelengths is generated, thus forming a continuous spectrum [4]
- The generation of a continuous spectrum can also be explained from quantum theory, which believes that electrons outside the nucleus move in atomic orbits and are at different discrete energy levels. When N atoms are close to each other, due to the interaction between the atoms, a slight change in the energy of the atomic orbital will occur, resulting in the overlap of the atomic orbital and the phenomenon of energy level splitting. Energy levels with the same energy in N atoms will split into N energy levels with slightly different energies. Because the number of atoms is extremely large (N = 10 19 to 10 21 / mm 3 ), the difference between the N split energy levels is so small that it can be regarded as a continuous distribution, that is, an energy band with a certain width is formed.
- There are any two energy bands Em and E n (E m > E n ), and the energy band width is E m = E mt -E mb (t represents the energy band top; b represents the energy band bottom; the same applies hereinafter); E n = E nt -E nb , and the spectral selection law is satisfied between the two energy bands, when a radiative transition occurs between the two energy bands, the radiation spectral line will be broadened to a spectral band, and the Partial overlap forms a continuous spectrum. Due to the strong attraction of the nucleus to the inner orbiting electrons and the shielding effect of the outer orbiting electrons, the inner electrons hardly participate in the transition of the outer electrons, so this phenomenon of broadening the corresponding spectral line due to the band structure mainly corresponds to The transition of the electrons in the outer orbit of the atom, so its spectrum is mainly distributed in the infrared, visible, and ultraviolet regions, and its short-wave part overlaps with soft X-rays.
- The supercontinuum laser can be described by "the spectral width of the incandescent lamp and the brightness of the laser". The discovery of supercontinuum lasers was discovered in an accidental experiment. The original purpose of irradiating crystals such as calcite with lasers was to determine the lifetime of phonons in the crystals, but the generation of white lasers was observed. The input green laser pulse has some interaction with the medium, which causes the laser's frequency range to be sharply broadened. Later, liquid and gaseous media were also tried to use supercontinuum laser technology, which extended the spectrum of supercontinuum laser to the infrared band.
- There are two main reasons for the generation of supercontinuum lasers in optical fibers. One is that the self-phase modulation effect is the main reason for the generation of supercontinuum lasers, and the other is that the supercontinuum lasers are self-phase modulation and four-wave mixing. The results of the combined effects of frequency and cross-phase modulation, but neither of these two theories has been reported systematically.
- Supercontinuum lasers generated in optical fibers have been widely used. The most important and mature among them are ultra-precise frequency measurement and precision clocks.
- There is indeed a discontinuous steady-state energy level distribution inside the atom. The energy level interval decreases with the increase of the quantum number n, and the transition of electrons between the energy levels produces a linear spectrum. n =