Theory of Molecular Quantum Dynamics in High-Harmonic Generation

高次谐波产生的分子量子动力学理论

• 批准号: 32482120
• 负责人: Professor Dr. Manfred Lein
• 金额: --
• 依托单位: Institut für Theoretische Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/32482120?language=en
• 关键词: Theory; Molecular; Quantum; Dynamics; Harmonic

Intensive research efforts are currently devoted to high-harmonic generation, i.e. the generation of high-frequency photons by laser irradiation of atoms or molecules. In the widely accepted three-step model, harmonic radiation originates from a sequence of ionization, free acceleration of the electron in the laser field, and recollision with the core. This recollision is of great interest since it allows to probe the state of a molecule with its own electron. Previously, the influence of molecular dynamics on high-harmonic generation was described in an approximation where only the active electron feels the laser force while the dynamics of the core is field free. Here, we develop a theory to overcome this limitation and take the interaction of the molecular core with the laser field into account. This involves the propagation of nuclear wave packets in laser-coupled Born-Oppenheimer surfaces. The approach is applicable to diatomic as well as polyatomic molecules. The signatures in the harmonic spectrum due to nuclear motion contain information on the instantaneous laser-induced distortion of Born-Oppenheimer potentials, thus providing a way to investigate these distortions experimentally. We investigate schemes to control high harmonic generation by exploiting the nuclear motion. Predictions of harmonic spectra not only for the usual Ti:Sapphire laser wavelength but also for longer infrared wavelengths are planned.

目前，大量的研究工作致力于高次谐波的产生，即通过激光照射原子或分子来产生高频光子。在被广泛接受的三步模型中，谐波辐射源于一系列电离、电子在激光场中的自由加速以及与核心的再碰撞。这种再碰撞是非常有趣的，因为它允许用自己的电子探测分子的状态。以前，分子动力学对高次谐波产生的影响是在一个近似的情况下描述的，即只有活跃的电子感受到激光的力，而核心的动力学是无场的。在这里，我们发展了一种理论来克服这一限制，并考虑了分子核与激光场的相互作用。这涉及到核波包在激光耦合的Born-Oppenheimer表面中的传播。该方法既适用于双原子分子，也适用于多原子分子。由原子核运动引起的谐波谱中的信号包含了激光诱导的Born-Oppenheimer势的瞬时失真的信息，从而提供了一种从实验上研究这些失真的方法。我们研究了利用原子核运动来控制高次谐波产生的方案。不仅对通常的钛宝石激光波长，而且对更长的红外波长，都计划进行谐波光谱的预测。