Control of Molecular Quantum State Character by Coherence Effects

Marjatta Lyyra在坦普尔大学的研究小组得到了原子、分子和光学物理计划的支持，在频域内开展了一系列关于光与小分子相互作用的基础研究。她的团队开发了量子光学在分子系统中的应用，包括电磁诱导透明和Autler-Townes(AT)效应。这些研究促进了量子光学研究向以实际应用为目标的分子系统的转变。复杂的分子能级结构、分子相互作用和弛豫路径为控制分子动力学和量子态性质提供了丰富的相干效应测试基础。例如，通过实验和理论相结合的研究，她的研究小组已经展示了对分子角动量排列的控制。Autler-Townes效应的另一个重要应用是将其用作核间距离相关的跃迁偶极矩函数的精确探针，该函数是光与分子相互作用的核心。这些测量依赖于对控制激光跃迁线形的Autler-Townes分裂的测量，以及对该激光器电场幅度的准确测量。AT效应的另一个应用涉及外部光学控制一对紧密间隔的分子单重态和三重本征态之间的混合，这些本征态受到自旋-轨道相互作用的弱扰动。AT效应导致标称单线态能级分裂成一对场修改能级，其中一个调子更接近三重态，导致单重态-三重态混合增加，另一个远离三重态，导致单重态-三重态混合减少。因此，这种光学控制机制可以用来调节自旋-轨道混合系数，从而控制量子态的单态和三态特性。除了开发量子干涉和相干效应的新应用外，这项研究还连接了传统上分离的研究领域：一方面是分子光谱学和动力学，另一方面是量子光学和控制。由于这项研究的基本性质，这些结果具有广泛的适用性。例如，寻找形成超冷分子的最佳激发途径，以及价电子自旋极化在光化学中的作用。在这个项目中，年轻科学家，其中许多是女性，参与本科生、研究生和博士后水平的前沿科学研究，从而为他们未来参与科学和技术工作积累关键经验和信心。

Marjatta Lyyra's research group at Temple University is supported by the Atomic, Molecular and Optical Physics Program to carry out a series of fundamental studies of the interaction of light with small molecules in the frequency domain. Her group has developed applications of quantum optics for molecular systems including electromagnetically induced transparency and the Autler-Townes (AT) effect. These studies have facilitated a shift of quantum optics studies to molecular systems with practical applications as the goal. The complex molecular energy level structure, molecular interactions, and relaxation pathways provide a rich testing ground of coherence effects for controlling molecular dynamics and quantum state character. Through combined experimental and theoretical studies her research group has demonstrated control of molecular angular momentum alignment, for example. Another important application of the Autler-Townes effect is its use as a precision probe of the internuclear distance-dependent transition dipole moment functions, which are at the heart of the interaction of light with molecules. These measurements rely on the measurement of the Autler-Townes splitting from the lineshape of the control laser transition combined with an accurate measurement of the electric field amplitude of this laser. Another application of the AT effect involves external optical control over the mixing between a pair of closely-spaced molecular singlet and triplet eigenstates that are weakly perturbed by the spin-orbit interaction. The AT effect causes the nominal singlet level to split into a pair of field modified levels, one of which tunes closer to the triplet, resulting in increased singlet-triplet mixing, and the other farther from the triplet, resulting in decreased singlet-triplet mixing. Thus this optical control mechanism can be used to "tune" the spin-orbit mixing coefficients and as a result control quantum state singlet and triplet character.In addition to developing new applications of quantum interference and coherence effects, this research bridges traditionally separate research communities: molecular spectroscopy and dynamics on one hand, and quantum optics and control on the other hand. Due to the fundamental nature of this research the results are broadly applicable. Examples include finding optimal excitation pathways for ultracold molecule formation and role of valence electron spin polarization in photochemistry.In this project, young scientists, many of whom are women, participate in forefront scientific research at the undergraduate, graduate and postdoctoral levels and as a result develop critical experience and confidence for their future participation in the scientific and technical workforce.