Section V Formation of bright and dark line spectra of atoms
Types of atomic spectra. There are two types of atomic spectrum, namely bright line spectrum (emission spectrum) and dark line spectrum (absorption spectrum). It is generally thought that electrons in an atom will fission and release photons when they return from orbits farther away from the nucleus to orbits closer to the nucleus, and a photon will be emitted when an electron fission, and the light emitted by a large number of excited atoms will form several specific bright lines, called bright line spectra or emission spectra.
When the light emitted by the high-temperature object (including the continuous wavelength change of light) passes through the substance, some specific wavelengths of light will be absorbed by the substance, so that the corresponding dark line or dark band will appear on the background of the continuous spectrum, this spectrum is called absorption spectrum, also called dark line spectrum. For example, let the white light from the arc lamp pass through the low temperature sodium vapor (put some salt on the center of the alcohol lamp, salt will be decomposed by heat to produce sodium vapor), and then observe with the spectroscope, you will see in the background of the continuous spectrum there are two dark lines very close together, which is the absorption spectrum of sodium atoms. It is particularly important to point out that each dark line in the absorption spectrum of each atom corresponds to a bright line in the emission spectrum of that atom, which indicates that the light absorbed by the cold gas atom is exactly the light emitted by this atom at high temperatures. Therefore, the spectral lines in the absorption spectrum (dark lines) are also the characteristic spectral lines of atoms, but usually fewer characteristic spectral lines are seen in the absorption spectrum than in the bright line spectrum.
Formation of atomic absorption spectrum (dark line spectrum). Our previous analysis pointed out that the electrons bound by the electrostatic gravity of the nucleus are in a state of hunger, their mass is smaller than the mass of the free electrons, the internal binding force is larger, and the affinity for photons is strong, so they have the possibility of absorbing photons, but the possibility of absorbing photons does not mean that it will definitely absorb photons. Because electrons are constantly torn apart by the electrostatic gravity of the nucleus in the atom, this tearing effect always causes the electron to undergo deformation and fission to release photons. If the mass of the electron in a stable orbit is M, then the electron must be in a peak mass-binding energy state, that is to say, the binding energy inside the electron is very large. If the electron absorbs a photon with a mass of m and forms a new electron with a mass of (M+m), If the new electron of mass (M+m) is not at another peak of the mass-binding energy curve (which often happens because the magic number of electron masses is only a few discontinuous points), then the internal binding force of the new electron of mass (M+m) will not be very large. It may even be much, much smaller than the internal binding force of the mass M electron (or even several orders of magnitude smaller), because the internal binding force of the new mass (M+m) electron is not enough to resist the electrostatic pull of the nucleus, so the newly generated electron is unstable and will quickly "fission" to release the mass m photon. If this action time is very short, from another point of view, it can be considered that the electron cannot absorb this mass of m photons, and it can be considered that the electron hardly absorbs such photons.
According to the mass-binding energy curve of the electron, we know that for an electron of a certain mass in a certain orbit, it can only absorb one or several photons of a certain mass. For example, if the mass of the electron in the closest orbit to the nucleus is 10000 at the beginning, the mass of the photon can be continuously changed from 1 to 1000, and the magic number corresponding to the maximum value of the electron binding energy is 10000, 10030, 100080, 10160, 10330, etc. If there is natural light at this time - photons of continuous mass (energy) change (their mass from 1 to 1000 continuous change) shine on the atom, then at this time the electron is most likely to absorb photons of what mass? Obviously, the absorption rate of electrons is the highest for photons with masses of 30, 80, 160 and 330. Because the electrons combined with these photons form electrons with masses of 10030, 10080, 10160, 10330, respectively, these electrons are relatively stable and the internal binding force is large enough to resist the electrostatic gravity of the nucleus. After the continuous light from 1 to 1000 passes through the atom, several dark lines appear in the continuous spectrum, and these dark lines correspond to photons with masses of 30, 80, 160, and 330.
To continue the previous discussion, when a beam of light passes through an atom, the electron will only absorb photons with masses of 30, 80, 160, and 330, and for other masses, the electron will hardly absorb, or the absorption rate will be very low. When the electron absorbs the mass of 30, 80, 160, 330 photons, the formed new electron mass is 10030, 10080, 10160, 10330, etc., and the mass of 10030 electrons will absorb the mass of 50, 130, 300 photons. An electron with a mass of 10080 will absorb an electron with a mass of 80 and 250, an electron with a mass of 10160 will absorb an electron with a mass of 170, and eventually an electron with a mass of 10,000 will absorb a photon with a mass of 30, 80, 160, 330, 50, 130, 300, 250, 170.
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