二氧化碳中Renner-Teller混合中性振动电子态的电子对称性与飞秒相干动力学
Electronic Symmetry and Femtosecond Coherence Dynamics of Renner-Teller-Mixed Neutral Vibronic States in Carbon Dioxide
- Purdue University（普渡大学）
- National Research Council of Canada（加拿大国家研究委员会）
- University of Mary Washington（玛丽华盛顿大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用真空紫外瞬态吸收光谱，通过分子框架各向异性分辨二氧化碳中Renner-Teller分裂的振动电子态对称性，并测量其对称性相关的相干退相时间，揭示激发态势能面拓扑对超快波包动力学的影响。
AI中文摘要：
当非绝热耦合混合分子的电子态时，不同电子对称性的振动电子态会在同一光谱区域内交错分布。由于取向平均，常规光谱学无法获取这些态的对称性。我们证明，即使不同对称性的态在能量上重叠，分子框架角向特征仍得以保留，可用于分辨这些态。利用对准的二氧化碳分子的真空紫外瞬态吸收光谱，我们分离出由$^1\Delta_u$态的Renner-Teller分裂产生的两类电子性质不同的振动电子态（$A^{'}$和$A^{''}$）。我们连续重构振动电子流形上的分子框架各向异性，显示各向异性从垂直跃迁特征跨越到平行跃迁特征，并映射出交错的电子对称性景观。通过扫描真空紫外脉冲与近红外脉冲之间的飞秒延迟至时间重叠区域，我们测量了这些态与对称性相关的相干退相时间，发现平行（$A^{'}$）态的退相快于垂直（$A^{''}$）态。我们将其归因于$A^{'}$激发态势能面独特的拓扑结构导致$A^{'}$波包更快离开Franck-Condon区域。这些测量探测了耦合激发态势能面上对称性分辨的超快波包动力学。
英文摘要：
When non-adiabatic coupling mixes electronic states of a molecule, vibronic states of different electronic symmetry become interleaved across the same spectral region. The symmetry of these states cannot be accessed in conventional spectroscopy due to orientation averaging. We show that molecular-frame angular signatures, which are preserved even when states with different symmetry overlap in energy, can be used to resolve them. Using vacuum-ultraviolet transient absorption spectroscopy of aligned carbon dioxide molecules, we separate two electronically distinct classes of vibronic states ($A^{'}$ and $A^{''}$) that arise from Renner-Teller splitting of the $^1Δ_u$ state. We reconstruct molecular-frame anisotropy continuously across the vibronic manifold showing that the anisotropy crosses over from perpendicular to parallel transition character and maps the interleaved electronic symmetry landscape. By scanning the femtosecond delay between the VUV and a near-infrared pulse through temporal overlap, we measure symmetry-dependent coherence dephasing times of these states and find that the parallel ($A^{'}$) states dephase faster than the perpendicular ($A^{''}$) states. We attribute this to faster departure of the $A^{'}$ wavepacket from the Franck-Condon region due to the distinct topology of the $A^{'}$ excited-state surface. These measurements probe symmetry-resolved ultrafast wavepacket dynamics on the coupled excited-state potential energy surfaces.
