Nardi Alessandro Nicola, Boyer Alexie, Hu Yaowei, Loriot Vincent, Lépine Franck, Vacher Morgane, Nandi Saikat
Nantes Université, CNRS, CEISAM, UMR 6230, F-44000, Nantes, France.
Universite Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, UMR 5306, F-69100, Villeurbanne, France.
Commun Chem. 2025 Jul 31;8(1):222. doi: 10.1038/s42004-025-01621-z.
Symmetry governs nature's laws, yet many of the natural phenomena occur due to the breakdown of symmetry. Here, we show how isotope-induced inversion symmetry breaking influences ultrafast photoisomerization processes in ethylene. Using extreme ultraviolet pump - near infrared probe time-of-flight mass spectrometry, we find that replacing one of the carbon atoms in ethylene with a C isotope leads to twice-faster structural relaxation via ethylene-ethylidene isomerization in the photo-excited molecular cation. Advanced trajectory surface hopping calculations incorporating the nuclear symmetry of the molecular systems, reveal that it arises from the mixing of different normal modes in the isotope-substituted species, interactions otherwise forbidden by symmetry. Although the mixing does not alter the symmetry of the electronic Hamiltonian, it modifies that of the nuclear Hamiltonian, causing explicit symmetry breaking. This facilitates efficient intra-molecular vibrational energy redistribution, lowering the isomerization yield. Our findings offer opportunities to use isotope-induced nuclear symmetry breaking to control the outcome of light-molecule interactions across ultrafast timescales.
对称性支配着自然规律，但许多自然现象却是由于对称性破缺而发生的。在此，我们展示了同位素诱导的反演对称性破缺如何影响乙烯中的超快光异构化过程。使用极紫外泵浦-近红外探测飞行时间质谱，我们发现用碳同位素取代乙烯中的一个碳原子会导致光激发分子阳离子通过乙烯-亚乙基异构化实现结构弛豫速度加快两倍。结合分子系统核对称性的先进轨迹表面跳跃计算表明，这是由于同位素取代物种中不同简正模式的混合所致，这种相互作用在对称性方面原本是被禁止的。尽管这种混合不会改变电子哈密顿量的对称性，但它改变了核哈密顿量的对称性，导致明显的对称性破缺。这促进了分子内振动能量的有效重新分布，降低了异构化产率。我们的研究结果为利用同位素诱导的核对称性破缺来控制超快时间尺度上光分子相互作用的结果提供了机会。
