A time averaged semiclassical approach to IR spectroscopy.

Area of Science:

• Chemical Physics
• Computational Chemistry
• Molecular Spectroscopy

Background:

• Calculating molecular infrared (IR) spectra is crucial for understanding molecular properties and dynamics.
• Existing semiclassical methods may face challenges in accuracy and applicability to complex systems.

Purpose of the Study:

• To introduce a novel semiclassical approach for computing molecular IR spectra.
• To validate the method's accuracy and applicability across different temperature regimes and molecular systems.

Main Methods:

• Employing a time averaging technique on a symmetrized quantum dipole-dipole autocorrelation function.
• Investigating spectra at both high and low temperatures.
• Applying the method to water and carbon dioxide (CO2) molecules.

Main Results:

• Accurate reproduction of the IR spectrum for water, with intensities within 4% of exact values.
• Identification of potential hot bands in high-temperature spectra.
• Demonstrated ability to distinguish between IR and power spectra for CO2, correctly identifying active IR transitions.

Conclusions:

• The new semiclassical method offers excellent accuracy for calculating IR absorption intensities and vibrational frequencies.
• The approach is versatile, applicable to various temperatures and molecular systems.
• Future work can integrate this method with advanced techniques for complex molecular systems.