根据量子力学微扰理论给出了在相干激发电离情形下双光子共振三光子近共振和双光子近共振三光子共振这两种四光子电离过程的电离截面表达式,表明这两种过程的离子强度与它们的起始能级有关。根据这一结论分析了实验测得的对氟甲苯分子的多光子电离谱,结果表明获得该电离谱的过程为三光子共振四光子电离过程。

Based on the pertubation theory of quantum mechanics, the formula of ionizing cross-section of the four- photon ionization processes with either two- photon resonance three-photon near- resonance or three- photon resonance two- photon nearresonane is derived under the condition of coherent exciting ionization. The result implies that the ion intensities of the two processes above relate to the molecular population on the initial energy levels that the processes concern. The four-photon ionization spectra are experimentally measured and analyzed with this result, which shows that the ionization process is one with three-photon resonance.