Energy difference between the lowest doublet and quartet states states of the boron atom

TL;DR

This paper accurately calculates the energy differences between the lowest doublet and quartet states of boron using advanced computational methods, revealing that existing database values are underestimated by over 300 cm$^{-1}$.

Contribution

It provides highly precise theoretical energy calculations for boron's low-lying states, including relativistic and finite mass effects, addressing unmeasured energy differences.

Findings

Calculated energy differences with Hartree accuracy.

Found existing database excitation energies are underestimated.

Highlights the need for revised spectroscopic data.

Abstract

The energies of the lowest $^2P_u$, $^4P_g$ and $2D_g$ states of the boron atom are calculated with $\mu$hartree accuracy, in the basis of symmetrized, explicitly correlated Gaussian lobe functions. Finite nuclear mass and scalar relativistic corrections are taken into account. This study contributes to the problem of the energy differences between doublet and quartet states of boron, which have not been measured to date. It is found that the $^2P_u\rightarrow^4P_g$ excitation energy, recommended in the Atomic Spectra Database, appears underestimated by more than 300~cm$^{-1}$.