Electronic Symmetry and Femtosecond Coherence Dynamics of Renner-Teller-Mixed Neutral Vibronic States in Carbon Dioxide
Abstract
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 1Δu 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.
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BibTeX
@misc{liu2026electronic,
title = {{Electronic Symmetry and Femtosecond Coherence Dynamics of Renner-Teller-Mixed Neutral Vibronic States in Carbon Dioxide}},
author = {Eric Liu and Shashank Kumar and Siddhant Pandey and Tzu-Hsien Tan and Russell Zimmerman and Kousik Bera and Anthony Fiore and Paul Hockett and Varun Makhija and Niranjan Shivaram},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.00565},
eprint = {2610.00565},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.00565},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Electronic Symmetry and Femtosecond Coherence Dynamics of Renner-Teller-Mixed Neutral Vibronic States in Carbon Dioxide
AU - Eric Liu
AU - Shashank Kumar
AU - Siddhant Pandey
AU - Tzu-Hsien Tan
AU - Russell Zimmerman
AU - Kousik Bera
AU - Anthony Fiore
AU - Paul Hockett
AU - Varun Makhija
AU - Niranjan Shivaram
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.00565
UR - https://arxiv.org/abs/2610.00565
AB - 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.
ER -