The basic principle of the spectrum analyzer
Shanghai Wujiu Automation Equipment Co., Ltd. First, the generation of atomic spectra
Atomic emission spectroscopy is the determination of the chemical composition of a substance based on the spectrum emitted by the atom. Different substances are composed of atoms of different elements, and the atoms contain a tightly structured nucleus surrounded by electrons that move continuously. Each electron is at a certain energy level and has a certain amount of energy. Under normal conditions, the atom is in a stable state and its energy is the lowest. This state is called the ground state. But when an atom is subjected to energy (such as heat, electricity, etc.), the atom acquires energy by colliding with high-speed moving gaseous particles and electrons, causing the electrons in the outer layer of the atom to transition from the ground state to a higher energy level. An atom in this state is called an excited state. The energy required for an electron to transition from a ground state to an excited state is called an excitation potential. When the applied energy is large enough, the electrons in the atom are separated from the nucleus and the atom becomes an ion. This process is called ionization. The energy required for an atom to lose an electron to become an ion is called the first-order ionization potential. The outer electrons in the ions can also be excited, and the energy required is the excitation potential of the corresponding ions. The atoms in the excited state are very unstable and transition to the ground state or other lower energy levels in a very short time.
When an atom transitions from a higher energy level to a ground state or other lower energy level, excess energy is released, which is radiated in the form of electromagnetic waves of a certain wavelength, and the energy of the radiation can be expressed by the following formula :(
1 )
E2 ,
E1 High energy level, low energy level,
h Planck
Planck )constant;
v And λ are the frequency and wavelength of the emitted electromagnetic wave, respectively.
c For the speed of light in a vacuum.
The wavelength of each line emitted depends on the difference between the two energy levels before and after the transition. Since the atom has many energy levels, the outer electrons can have different transitions after being excited, but these transitions should follow certain rules (ie, "spectral law"), so a series of atoms for a particular element can produce a series of Characteristic spectral lines of different wavelengths, which are arranged in a certain order and maintain a certain intensity ratio. Spectral analysis is to identify the presence of elements (qualitative analysis) by identifying the characteristic spectra of these elements, and the intensity of these spectral lines is related to the content of the elements in the sample, so the intensity of these lines can be used to determine the elements. Content (quantitative analysis). This is the basic basis for emission spectroscopy.
Second, the process of emission spectrum analysis
1
. The sample is evaporated, atomized (converted into a gaseous atom) by the action of energy, and the outer electrons of the gaseous atom are excited to a high energy state. When transitioning from a higher energy level to a lower energy level, the atom will release excess energy and emit a characteristic line. This process is called evaporation, atomization, and excitation and is achieved by means of an excitation source.
2
. The radiation generated by the atoms is dispersively split and recorded on the photosensitive plate in order of wavelength, and a regular spectral line, that is, a spectrogram, is presented. This is achieved by means of a spectroscopic and detection device of the spectrograph.
3
. Qualitative or quantitative analysis is performed based on the obtained spectrum. Due to the different atomic structures of different elements, the wavelengths of the emission spectral lines are different when excited, that is, each element has its characteristic wavelength, so according to the characteristic spectrum of these elements, the existence of the element can be accurately identified (qualitative) Analysis), and the intensity of these spectral lines is related to the content of this element in the sample, so the intensity of these lines can be used to determine the content of the elements (quantitative analysis).