Vibronic coherent quantum beat in four-layer platinum carbonyl cluster

Area of Science:

• Physical Chemistry
• Quantum Mechanics
• Spectroscopy

Background:

• Vibronic coherence is crucial for understanding molecular dynamics.
• Direct experimental and theoretical comparisons of vibronic coherence are scarce.
• Platinum carbonyl clusters exhibit complex electronic and vibrational interactions.

Purpose of the Study:

• To investigate the vibronic coherent quantum beat in a platinum carbonyl cluster, [Pt3(CO)6]42-.
• To compare experimental observations with theoretical models for vibronic coherence.
• To elucidate the mechanisms behind quantum beat frequencies, node positions, and amplitude asymmetry.

Main Methods:

• Femtosecond vis-pump/vis-probe transient absorption spectroscopy.
• Selective preparation of quantum beats coupled to electronic ground and excited states.
• Quantum chemistry calculations and theoretical model calculations using the doorway-window approach.

Main Results:

• Observed distinct quantum beats (41 cm-1 at ground state, 28 cm-1 at excited state) with unique phase behaviors.
• Asymmetric beat amplitudes were noted, differing between ground and excited states.
• Theoretical models successfully explained frequency differences, node positions, and amplitude asymmetry, linking them to vibronic coupling and Franck-Condon factors.

Conclusions:

• Vibronic coupling between cluster motions and electronic excitation drives observed quantum beats.
• The Herzberg-Teller and Franck-Condon terms are critical for different electronic states.
• Theoretical insights provide a general framework for interpreting vibronic coherence in molecular systems.