High-harmonic spectroscopy driven by circularly polarized laser pulses and their counterrotating second harmonic is a new branch of attosecond science which currently lacks quantitative interpretations. We extend this technique to the midinfrared regime and record detailed high-harmonic spectra of several rare-gas atoms. These results are compared with the solution of the Schrödinger equation in three dimensions and calculations based on the strong-field approximation that incorporate accurate scattering-wave recombination matrix elements. A quantum-orbit analysis of these results provides a transparent interpretation of the measured intensity ratios of symmetry-allowed neighboring harmonics in terms of (i) a set of propensity rules related to the angular momentum of the atomic orbitals, (ii) atom-specific matrix elements related to their electronic structure, and (iii) the interference of the emissions associated with electrons in orbitals corotating or counterrotating with the laser fields. These results provide the foundation for a quantitative understanding of bicircular high-harmonic spectroscopy.

中文翻译：

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双圆高谐波光谱学中电子结构的特征

由圆偏振激光脉冲及其反向旋转的二次谐波驱动的高谐波光谱学是阿秒科学的一个新分支，目前尚缺乏定量解释。我们将此技术扩展到中红外范围，并记录了几种稀有气体原子的详细高谐波光谱。将这些结果与Schrödinger方程的解在三维上进行了比较，并在强磁场近似的基础上进行了计算，并结合了精确的散射波重组矩阵元素。这些结果的量子轨道分析提供了一种透明的解释，即根据（i）与原子轨道的角动量有关的一组倾向性规则，来测量对称允许的相邻谐波的强度比，（ii）与原子的电子结构有关的特定于原子的基质元素，以及（iii）与激光场同向或反向旋转的轨道中与电子有关的发射的干扰。这些结果为定量理解双圆高谐波光谱学提供了基础。