Transient Two-Dimensional Infrared Spectroscopy in a Vibrational Ladder

Area of Science:

• Chemical Physics
• Spectroscopy
• Molecular Dynamics

Background:

• Carboxyhemoglobin (COHb) is a key molecule in understanding hemoglobin function.
• Vibrational spectroscopy provides insights into molecular structure and dynamics.
• Non-equilibrium conditions are crucial for studying energy relaxation pathways.

Purpose of the Study:

• To investigate vibrational energy flow in carboxyhemoglobin using transient 2D spectroscopy.
• To analyze the spectral signatures of vibrational ladder climbing.
• To understand the dynamics of population relaxation in excited vibrational states.

Main Methods:

• Transient two-dimensional Fourier transform infrared spectroscopy (2DIR).
• Induction of vibrational ladder climbing in the CO-moiety longitudinal stretch.
• Analysis of spectral peak assignments based on vibrational anharmonicity.

Main Results:

• Observation of a non-equilibrium 2DIR spectrum with numerous peaks.
• Assignment of spectral peaks to specific vibrational transitions up to seven levels.
• Evidence of population distribution across multiple vibrational levels.

Conclusions:

• The anharmonicity of the vibrational potential facilitates the identification of individual transitions.
• Transient 2DIR spectroscopy is a powerful tool for probing non-equilibrium vibrational dynamics.
• Understanding population relaxation is key to deciphering energy transfer mechanisms in molecules like COHb.