Transient Symmetry Controls Photo Dynamics near Conical Intersections

• Published in: The journal of physical chemistry letters Vol. 12; no. 38
• Main Authors: Waters, Max D. J., Du, Wenpeng, Carrascosa, Andres Moreno, Stankus, Brian, Cacciarini, Martina, Weber, Peter M., Sølling, Theis I.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16.09.2021
• Subjects: ATOMIC AND MOLECULAR PHYSICS; coherence; energy; group theory; molecules; nanoelectromechanical systems; non-statistical; oscillation; photo electron spectroscopy; Rydberg State; ultrafast
• ISSN: 1948-7185; 1948-7185

Excited-state chemistry lacks generalised symmetry rules. With many femtochemistry studies focused on individual cases, it is hard to build up the same level of chemical intuition for excited-states as exists for ground states. Here, we unravel the degrees of freedom involved in ultrafast internal conversion (IC) by mapping the vibrational coherence of the initial wavepacket, and the dependence on molecular symmetry in various cyclic tertiary amines. Molecular symmetry plays an important role in the preservation of vibrational coherence in the transit from one electronic state to another. We show here that it is sufficient for the molecule to simply have the possibility of a more symmetric structure to achieve the preservation of vibrational coherence. It can be transient and still lead to preservation. Furthermore, this finding provides an additional angle on how symmetry influences electronic transitions and an additional piece to the puzzle of establishing symmetry-based selection rules for excited-state processes.