Observing vibronic coupling in a strongly hydrogen bonded system with coherent multidimensional...

Area of Science:

• Physical Chemistry
• Spectroscopy
• Chemical Dynamics

Background:

• Intramolecular hydrogen bonding is crucial for ultrafast chemical reactions like proton transfer.
• Understanding the interplay between vibrational and electronic states is key to elucidating reaction mechanisms.

Purpose of the Study:

• To investigate the coupled structural and electronic parameters in the ultrafast proton transfer system 10-Hydroxybenzo[h]quinoline (HBQ).
• To analyze the vibrational-electronic couplings using advanced spectroscopic techniques.

Main Methods:

• One- and two-dimensional vibrational-electronic (1D and 2D VE) spectroscopy experiments were conducted.
• Fourier analysis was employed to study coherent oscillations in vibrational modes.
• Polarization-selective 1D VE experiments were used to probe orientation-dependent couplings.

Main Results:

• The OH stretch (νOH) mode shows strong coupling to the electronic excitation in HBQ.
• Low-frequency modes (242 and 386 cm-1) modulate the electronic signal by altering hydrogen bond distance.
• Evidence of direct coupling between the νOH mode and the S1 ← S0 electronic transition was observed.

Conclusions:

• Multidimensional VE spectroscopy provides a quantitative understanding of vibronic coupling in HBQ.
• These findings highlight the potential of VE spectroscopy for studying complex systems involving hydrogen bonding and ultrafast proton transfer.