The discharge tube of the CO2 laser is filled with a mixed gas of CO2, N2, He, etc., and its ratio and total gas pressure can vary within a certain range (generally: CO2:N2:He=1:0.5:2.5, total gas pressure is 1066.58pa). Any molecule has three different forms of motion. One is the movement of electrons in the molecule, which determines the energy state of the electrons. The second is the vibration of atoms in the molecule, that is, the atoms keep vibrating periodically around their equilibrium positions. This movement determines the vibration energy of the molecules. The third is the rotation of the molecules, which determines the rotation energy state of the molecules. The CO2 laser uses the transition between the vibration and rotation energy levels of the CO2 molecules to generate lasers.