Optimal internal coordinates, vibrational spectrum, and effective Hamiltonian for ozone

Area of Science:

• * Quantum Chemistry
• * Molecular Spectroscopy
• * Computational Chemistry

Background:

• * Understanding the vibrational spectrum of molecules like ozone (O3) is crucial for various chemical and physical applications.
• * Previous studies have explored ozone's vibrational properties, but accurate modeling remains a challenge.

Purpose of the Study:

• * To investigate the vibrational spectrum of ozone using optimal internal vibrational coordinates.
• * To determine an effective vibrational Hamiltonian that accurately describes the experimental frequencies.
• * To analyze the structure of the vibrational spectrum in terms of polyadic groups.

Main Methods:

• * Calculation of bound vibrational energy levels using variational methods and optimal internal coordinates.
• * Analysis of wave function expansion coefficients to identify spectral structure.
• * Development and fitting of an internal effective vibrational Hamiltonian using experimental data and perturbation theory.

Main Results:

• * Optimal internal coordinates efficiently converge vibrational energy levels with small anharmonic basis sets.
• * A significant portion of the ozone vibrational spectrum exhibits a polyadic structure characterized by the quantum number N.
• * The derived effective Hamiltonian accurately reproduces experimental vibrational frequencies in low and medium energy regimes.

Conclusions:

• * The use of optimal internal coordinates simplifies the accurate calculation of ozone's vibrational spectrum.
• * The identified polyadic structure provides a new way to understand and organize the spectrum.
• * The developed effective Hamiltonian offers a reliable tool for predicting ozone's vibrational behavior.