Attosecond spectroscopy reveals spontaneous symmetry breaking in molecular photoionization
- Mingxuan Li
- Leshi Zhao
- Huiyong Wang
- Jialong Li
- Wentao Wang
- Jiaao Cai
- Xiaochun Hong
- Xiaosen Shi
- Ming Zhang
- Xinning Zhao
- Robin Weissenbilder
- David Busto
- Mathieu Gisselbrecht
- Kiyoshi Ueda
- Sizuo Luo
- Zheng Li
- Dajun Ding
2025-09-19
Spontaneous symmetry breaking, driven by nonadiabatic electron-nuclear coupling, can lead to geometric complexity in molecules and solids. While structural distortion from symmetry breaking occurs in femtoseconds, the timescale to lift electronic state degeneracy has remained elusive. We use the vibrationally resolved attosecond chronoscope to capture the electronic symmetry breaking induced by the Renner-Teller effect in bent CO 2 molecules after photoionization by an extreme ultraviolet photon by measuring attosecond ionization delays. Relative photoionization delays between the four cation states are observed, with vibrational state–dependent delays, we analyze the evolution of the degenerate A 2 Π u state to the nondegenerate A ′ and A ″ states due to molecular bending. With the help of theoretical analysis, we show that the relative photoionization delays of up to 72 as between the vibrational levels originate from the symmetry breaking–induced shape resonance. This study offers fundamental insights by resolving the coupled electron and structural dynamics simultaneously.