Determine whether vibrational coherence transfers through the conical intersection

Determine whether the vibrational coherence of thymine’s high-frequency 1692 and 1710 cm⁻¹ modes, which drive the S2 (¹ππ*) to S1 (¹nπ*) internal conversion, is transferred through the conical intersection.

Background

The study observes coherent low-frequency vibrational motion, particularly the approximately 730 cm⁻¹ ring-breathing mode, and simulations indicate that this coherence survives the S2 to S1 internal-conversion process. In contrast, the higher-frequency 1692 and 1710 cm⁻¹ modes associated with bond-length-alternation motion drive the internal conversion itself and become experimentally unresolved because of the limited temporal resolution.

The authors explicitly state that they cannot determine whether coherence in these high-frequency modes is transferred through the conical intersection. Establishing this transfer would clarify how nuclear wave-packet coherence evolves during thymine’s ultrafast nonadiabatic relaxation.