Coherence specific signal detection via chiral pump-probe spectroscopy.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Quantum Dynamics

Background:

• Exciton coherence plays a crucial role in energy transfer processes within molecular systems.
• Understanding these dynamics requires advanced spectroscopic techniques capable of resolving ultrafast phenomena.
• Vibrational environments significantly influence exciton coherence, necessitating methods to disentangle these effects.

Purpose of the Study:

• To investigate transient circular dichroism (TRCD) spectroscopy for probing exciton coherence dynamics.
• To develop a theoretical framework for analyzing TRCD signals in pump-probe experiments.
• To demonstrate the potential of TRCD for unambiguously observing excited-state quantum coherence.

Main Methods:

• Theoretical modeling of transient circular dichroism (TRCD) spectroscopy.
• Utilizing a pump-probe configuration with variable polarization angles.
• Decomposition of the TRCD signal into chiral and achiral doorway and window functions.

Main Results:

• The chiral doorway component of the TRCD signal exhibits quantum beats related to excited-state dynamics.
• Comparison of signals at different pump-probe angles allows isolation of the chiral doorway function.
• The ground-state contribution to the chiral doorway function is minimal, especially with impulsive excitation.

Conclusions:

• Transient circular dichroism (TRCD) spectroscopy is a powerful tool for studying exciton coherence.
• The proposed pump-probe configuration in the impulsive limit can selectively probe excited-state quantum coherence.
• This technique offers a pathway to unambiguously investigate quantum coherence beating in molecular systems.