臭氧分子在激光场中的多光子激发

采用二次量子化方法和酉变换讨论了O3分子在激光场中的多光子激发.推导出了O3分子的振动Hamiltonian 算子、从基态到各激发态的跃迁几率公式,以及O3分子从激光场中吸收的光子数公式,并分析了计算结果.这包括对O3分子伸缩振动能谱的计算及与实验结果的比较,跃迁几率随外场频率的变化、随时间的变化,以及O3分子在辐射场中的能量吸收情况(取光场强度为5×10-2 W/cm2).建立讨论所有具有C2v对称分子从基态到第四激发态以下各态多光子激发问题的模型.

Multiphoton Excitation of an Ozone Molecule in Laser Fields

The multiphoton excitation of O3 molecules in laser fields is discussed using the second quantization and unitary transformations. It is successful to derive the total Hamiltonian (including the stretch-vibration Hamiltonian of an ozone molecule, the laser fields Hamiltonian and the interaction Hamiltonian between O3 and laser fields), the transition probabilities from the ground state to excited states and the expressions for the average number of photons absorbed by molecules from laser fields. The calculated stretch-vibration energy spectrum of O3 molecules is in good agreement with that of experiments. There are two peaks of single-photon transition at 1042.5 and 1103.0 cm-1, respectively. The three peaks of the two-photon transition are at 1027.5, 1055.5 and 1101.0 cm-1 respectively. The peaks at 1014.5, 1028.0, 1043.0 and 1100.5 cm-1 are four peaks of the three-photon transition. The amplitudes of the three-photon transition probability are about 6 orders of magnitude less than those of the two-photon transition which are about 14 orders of magnitude less than those of the single-photon transition. The laser field intensity is taken as 5×10-2 W/cm2, which is different from 109 W/cm2 in the former researches. This theoretical model can be used to discuss the multiphoton excitation for all of the molecules with a C2v symmetry, but inadequate to calculate the n-photon (n≥4) transition. In the computational process, it is found that the transition probability changes with the intensity of the laser field, which needs further research in the future.