Precision calculation of energy levels for four-valent Si I

TL;DR

This paper presents a high-precision calculation of the energy levels of neutral silicon (Si I) using advanced quantum methods, comparing two different approximations to achieve about 1% accuracy.

Contribution

It introduces a combined CI+MBPT approach for Si I and evaluates two different starting approximations, demonstrating comparable accuracy in energy level predictions.

Findings

Both $V^{N-2}$ and $V^{N-4}$ approximations yield similar accuracy (~1%).

The CI+MBPT method effectively calculates low-lying energy levels of Si I.

The approach enhances precision in atomic energy level calculations.

Abstract

We report results of the calculation of the low-lying levels of neutral Si using a combination of the configuration interaction and many-body perturbation theory (CI+MBPT method). We treat Si I as an atom with four valence electrons and use two different starting approximations, namely $V^{N-2}$ and $V^{N-4}$. We conclude that both approximations provide comparable accuracy, on the level of 1%.