Experimental oscillator strengths of Al I lines for near-infrared astrophysical spectroscopy

TL;DR

This study provides improved oscillator strengths for neutral aluminium lines in the near-infrared and optical spectra, aiding more accurate elemental abundance measurements in astrophysics, especially in obscured galactic regions.

Contribution

The paper presents new laboratory measurements of oscillator strengths for 12 aluminium lines in the NIR and optical, enhancing atomic data accuracy for astrophysical spectroscopy.

Findings

Oscillator strengths for 12 lines with 2-11% accuracy.

Branching fractions for 16 additional lines.

Improved atomic data for aluminium in NIR and optical regions.

Abstract

Elemental abundances can be determined from stellar spectra, making it possible to study galactic formation and evolution. Accurate atomic data is essential for the reliable interpretation and modeling of astrophysical spectra. In this work, we perform laboratory studies on neutral aluminium. This element is found, for example, in young, massive stars and it is a key element for tracing ongoing nucleosynthesis throughout the Galaxy. The near-infrared (NIR) wavelength region is of particular importance, since extinction in this region is lower than for optical wavelengths. This makes the NIR wavelength region a better probe for highly obscured regions, such as those located close to the Galactic center. We investigate the spectrum of neutral aluminium with the aim to provide oscillator strengths (f-values) of improved accuracy for lines in the NIR and optical regions (670 - 4200 nm). Measurements of high-resolution spectra were performed using a Fourier transform spectrometer and a hollow cathode discharge lamp. The f-values were derived from experimental line intensities combined with published radiative lifetimes. We report oscillator strengths for 12 lines in the NIR and optical spectral regions, with an accuracy between 2 and 11%, as well as branching fractions for an additional 16 lines.