Laser辐照下均质双原子中高次谐波的产生：分子强场近似的速度规范模型
High-Order Harmonic Generation in Laser-Irradiated Homonuclear Diatomics: The Velocity Gauge Version of Molecular Strong-Field Approximation
摘要：
在常规强场近似的速度规范下，研究了激光辐照下的光均方波（H2+，N2和O2）与原子（具有几乎相同的结合能）的高次谐波的产生.应用强场方法（我们以前发展的，在传统的鞍点近似之外加入了再散射效应），通过补充标准的原子轨道线性组合和分子轨道方法，目前被推广到分子情况。相关的模型被证明是充分再现的一般形状和详细的结构的分子谐波光谱，这表明了一些显着的显着的显着差异，从各自的原子光谱计算下相同的激光脉冲。所揭示的差异被发现是强烈依赖于核间的分离，也非常敏感的轨道和键的对称性贡献分子价壳。特别是，该模型正确地预测了高频平台的行为（无论是其程度，甚至结构的细节）在小（近平衡）和大的核间分离的分子谐波光谱。此外，对于一些组的谐波，谐波发射率被确定为占主导地位的贡献，从更高的结合能和不同的轨道对称性的最外层分子轨道相比，通常主要贡献的内分子壳。
英文摘要：
The generation of high harmonics in laser-irradiated light homonuclear diatomics (H2+, N2 and O2) compared to that in atomic counterparts (of nearly identical binding energy) is studied within the velocity gauge version of conventional strong-field approximation. The applied strong-field approach (we alternatively developed earlier to incorporate rescattering effects beyond the conventional saddle-point approximation) is currently extended to molecular case by means of supplement the standard linear combination of atomic orbitals} and molecular orbitals method. The associated model proved to adequately reproduce a general shape and detailed structure of molecular harmonic spectra, which demonstrate a number of remarkable distinctive differences from respective atomic spectra calculated under the same laser pulses. The revealed differences are found to be strongly dependent on internuclear separation and also very sensitive to the orbital and bonding symmetry of contributing molecular valence shell. In particular, the model correctly predicts the behavior of high-frequency plateau (both for its extent and even details of structure) in molecular harmonic spectra at small (nearly equilibrium) and large internuclear separations. In addition, for some group of harmonics, the harmonic emission rates were ascertained to dominate by contribution from inner molecular shells of higher binding energy and different orbital symmetry compared to the outermost molecular orbital normally predominantly contributing.
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