Highly Sensitive Non-linear Probes of Chiral Structure and Dynamics

手征性，即物体与其镜像的不可叠加性，在自然界中普遍存在，并且是描述自然过程的基础。对于手性分子，这种镜像对称性破缺导致分子的两个版本，左和右对映异构体，它们具有相同的化学和物理性质，除了与另一个手性物体如另一个手性分子或圆偏振光相互作用时。在时域中的手性分子的响应的日益增长的兴趣，激发了最近和正在进行的努力，以开发超快非线性手性光学技术，以实现这一目标。这一建议的目的是发展一种新的方法来观察相干激发态动力学的手性分子的理论基础。该方法是高度敏感的电子，振动和旋转的手征动力学，各种松弛过程，并失去连贯性。此外，这种方法提供了扩展到非手性分子的可能性，因为它可以诱导“外在”手性。在基于非线性光学参数过程的许多超快光谱学中，例如高次谐波产生和2D光谱学，检测到的信号对潜在动力学的相干性的灵敏度可能很低。这是因为这些参数过程导致表征潜在动力学的不同路径发生干扰，即使潜在动力学是不相干的。外在的手征应该允许一个克服这一限制，并制定超快的测量计划，是专门敏感的相干动力学。

Chirality, the non-superposability of an object with its mirror image, is ubiquitous in nature, and fundamental to the description of natural processes. For chiral molecules, this mirror-symmetry breaking leads to two versions of a molecule, the left and right enantiomers, which have identical chemical and physical properties except for when interacting with another chiral object such as another chiral molecule or circularly polarized light. The growing interest in the response of chiral molecules in the time domain has motivated recent and ongoing efforts to develop ultrafast non-linear chiroptical techniques to that aim. This proposal is aimed at developing the theoretical foundations of a novel approach to observing coherent excited state dynamics in chiral molecules. The approach is highly sensitive to electronic, vibrational and rotational chiral dynamics, to various relaxation processes, and to loss of coherence. Additionally, this approach offers the possibility of extension to non-chiral molecules as it can induce 'extrinsic' chirality. The sensitivity of the detected signal to the coherence of the underlying dynamics can be low in a number of ultrafast spectroscopies based on non linear optical parametric processes, such as, e.g. high harmonic generation and 2D spectroscopy. This is because these parametric processes cause the different pathways characterizing the underlying dynamics to interfere even if the underlying dynamics are incoherent. Extrinsic chirality should allow one to overcome this limitation and to develop ultrafast measurement schemes that are exclusively sensitive to coherent dynamics.