Extended transition rates and lifetimes in Al I and Al II from systematic multiconfiguration calculations

TL;DR

This paper presents comprehensive multiconfiguration calculations for aluminium's neutral and singly ionized states, providing highly accurate atomic data including energies, lifetimes, and transition probabilities, crucial for astrophysical applications.

Contribution

It offers the first systematic multiconfiguration Dirac-Hartree-Fock and RCI calculations for multiple states of Al I and Al II, significantly improving data accuracy over previous studies.

Findings

Calculated excitation energies agree well with NIST data.

Lifetimes match high-precision experimental measurements.

Updated transition data, especially in the infrared, enhance astrophysical modeling.

Abstract

Multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations were performed for 28 and 78 states in neutral and singly ionized aluminium, respectively. In Al I, the configurations of interest are $3s^2nl$ for $n=3,4,5$ with $l=0$ to $4$, as well as $3s3p^2$ and $3s^26l$ for $l=0,1,2$. In Al II, the studied configurations are, besides the ground configuration $3s^2$, $3snl$ with $n=3$ to $6$ and $l=0$ to $5$, $3p^2$, $3s7s$, $3s7p$ and $3p3d$. Valence and core-valence electron correlation effects are systematically accounted for through large configuration state function (CSF) expansions. Calculated excitation energies are found to be in excellent agreement with experimental data from the NIST database. Lifetimes and transition data for radiative electric dipole (E1) transitions are given and compared with results from previous calculations and available measurements, for both Al I and Al II. The computed lifetimes of Al I are in very good agreement with the measured lifetimes in high-precision laser spectroscopy experiments. The present calculations provide a substantial amount of updated atomic data, including transition data in the infrared region. This is particularly important since the new generation of telescopes are designed for this region. There is a significant improvement in accuracy, in particular for the more complex system of neutral Al I. The complete tables of transition data are available.