Finding Valence Antibonding Levels while Avoiding Rydberg, Pseudo-continuum, and Dipole-Bound Orbitals.

Area of Science:

• Computational Chemistry
• Quantum Chemistry

Background:

• Electronic structure methods are crucial for interpreting experimental data in chemistry.
• Valence antibonding orbitals (π* and σ*) are vital for understanding photochemical reactions, electron reductions, and reaction dynamics.
• Intruding orbitals (Rydberg, pseudo-continuum, dipole-bound) can complicate accurate population of target antibonding orbitals.

Purpose of the Study:

• To provide a practical method for correctly populating valence antibonding orbitals in electronic structure calculations.
• To address challenges posed by interfering molecular orbitals with similar energies.
• To enable accurate calculations of chemical processes involving these orbitals, particularly for metastable states.

Main Methods:

• Utilizing widely available electronic structure codes.
• Developing strategies to circumvent the influence of intruding orbitals.
• Incorporating electron correlation effects for high precision.

Main Results:

• A reliable procedure is demonstrated for populating valence π* and σ* orbitals.
• The method successfully avoids common pitfalls caused by interfering orbitals.
• Accurate calculations are achieved, offering chemically useful precision, especially for metastable electronic states.

Conclusions:

• The presented approach enhances the reliability of electronic structure calculations for critical chemical processes.
• Accurate population of valence antibonding orbitals is achievable even in the presence of complex orbital interactions.
• This methodology is valuable for studying reaction mechanisms and energy landscapes, particularly in photochemistry and electron-driven reactions.