Lowest ^{2}S Electronic Excitations of the Boron Atom

Area of Science:

• Quantum Chemistry
• Atomic Physics
• Theoretical Chemistry

Background:

• Accurate calculation of atomic bound states is crucial for understanding atomic structure and spectra.
• Existing methods often rely on approximations that limit accuracy, especially for systems with few electrons.

Purpose of the Study:

• To develop and implement a novel ab initio theoretical approach for calculating bound states of small atoms.
• To achieve high accuracy in determining electronic excitation energies for the boron atom.

Main Methods:

• Finite-nuclear-mass, non-Born-Oppenheimer (non-BO) nonrelativistic variational calculations.
• Utilizing all-particle explicitly correlated Gaussian functions.
• Incorporating leading relativistic and quantum electrodynamics (QED) energy corrections.

Main Results:

• The developed approach was applied to calculate total and transition energies for the lowest four ^{2}S electronic excitations of the boron atom.
• Calculated transition energies show excellent agreement with experimental values, within 0.2–0.3 cm⁻¹.
• This level of accuracy, previously limited to three- and four-electron systems, is now extended.

Conclusions:

• The new theoretical approach provides a highly accurate method for calculating atomic bound states and excitation energies.
• The demonstrated accuracy for the boron atom validates the non-Born-Oppenheimer approach with explicitly correlated Gaussian functions and QED corrections.
• This method opens possibilities for precise calculations on a wider range of atomic and molecular systems.