Capturing Coupled Structural and Electronic Motions During Excited-State Intramolecular Proton Transfer via...

Area of Science:

• Chemical Physics
• Spectroscopy
• Computational Chemistry

Background:

• Proton transfer is fundamental to many chemical reactions.
• Excited-state intramolecular proton transfer (ESIPT) is initiated by light, involving rapid proton movement.
• Understanding the coupled electronic and atomic motions during ESIPT is crucial for controlling chemical processes.

Purpose of the Study:

• To investigate time-dependent coupled atomic and electronic motions during and after ESIPT.
• To explore the utility of time-resolved resonant inelastic X-ray scattering (RIXS) for studying ultrafast chemical dynamics.
• To develop a method for correlating RIXS spectral features with proton transfer distances.

Main Methods:

• Performed excited-state ab initio molecular dynamics simulations.
• Calculated time-dependent density functional theory (TD-DFT) for a model ESIPT system (10-hydroxybenzo[h]quinoline).
• Computed transient RIXS spectra at nitrogen and oxygen K-edges.

Main Results:

• RIXS spectra provided detailed insights into local electronic structure and excited electronic state coupling.
• Observed reorganization of electronic structure synchronized with proton transfer.
• Developed a 'spectroscopic ruler' linking RIXS peak shifts to proton transfer distance.

Conclusions:

• Time-resolved RIXS is a powerful technique for probing coupled electronic and structural dynamics in ultrafast chemical processes.
• The study demonstrates RIXS's potential for detailed analysis of ESIPT mechanisms.
• Future experiments at soft X-ray free electron laser facilities can leverage this approach.