在不可约张量法基础上,利用二次量子化方法计算了原子的双光子激发截面.作为一个实例,计算了Hg原子的双光子激发截面.理论结果与实验结果在数量级上有较好的符合.

On the basis of the Irreducible tensor method, we use second quantization to calculate the two-photon excitation cross section. In the calculation, we suppose that two-photon process obeys parentage scheme approximation. On this condition, an approximation formula is developed to calculate two-photon excitation cross section of any atom. The theoretical formula can simplify the calculation process.As an illustrative example, we have calculated some two-photon excitation cross sections of Hg atom. The theoretioal results are in good agreement with experimental data on the order of magnitnde.