Progress in ultrafast science allows for probing quantum superposition states with ultrashort laser pulses in the new regime where several linear and nonlinear ionization pathways compete. Interferences of pathways can be observed in the photoelectron angular distribution and in the past they have been analyzed for atoms and molecules in a single quantum state via anisotropy and asymmetry parameters. Those conventional parameters, however, do not provide comprehensive tools for probing superposition states in the emerging research area of bright and ultrashort light sources, such as free-electron lasers and high-order harmonic generation. We propose a new set of generalized asymmetry parameters which are sensitive to interference effects in the photoionization and the interplay of competing pathways as the laser pulse duration is shortened and the laser intensity is increased. The relevance of the parameters is demonstrated using results of state-of-the-art numerical solutions of the time-dependent Schrödinger equation for ionization of helium atom and neon atom.

超快科学的进步允许在几个线性和非线性电离路径竞争的新机制中用超短激光脉冲探测量子叠加态。可以在光电子角分布中观察到路径的干扰，并且在过去，它们已经通过各向异性和不对称参数分析了单量子态的原子和分子。然而，这些常规参数并没有为在明亮和超短光源的新兴研究领域（例如自由电子激光器和高次谐波产生）中探测叠加态提供综合工具。我们提出了一组新的广义不对称参数，这些参数对光电离中的干扰效应和随着激光脉冲持续时间缩短和激光强度增加而竞争路径的相互作用敏感。使用氦原子和氖原子电离的时间相关薛定谔方程的最新数值解的结果证明了参数的相关性。