Atomic transitions for adaptive optics

TL;DR

This paper reviews atmospheric atomic and ionic species for their potential use in adaptive optics, focusing on their transition properties, excitation wavelengths, and suitability for laser guide star applications.

Contribution

It provides a comprehensive analysis of upper atmospheric atoms and ions, identifying promising candidates for adaptive optics laser guide stars based on their transition characteristics.

Findings

Na and Fe are prime candidates for polychromatic laser guide stars.

Ca$^+$ and Si$^+$ require excitation wavelengths beyond atmospheric cutoff.

O, N, and N$^+$ have high potential due to strong transitions and high abundance.

Abstract

This paper reviews atoms and ions in the upper atmosphere, including the mesospheric metals Na, Fe, Mg$^+$, Si$^+$, Ca$^+$, K and also non-metallic species N, N$^+$, O, H, considering their potential for astronomical adaptive optics. Na and Fe are the best candidates for the creation of polychromatic laser guide stars, with the strongest returns coming from transitions that can be reached by excitation at two wavelengths. Ca$^+$ and Si$^+$ have strong visible-light transitions, but require short wavelengths, beyond the atmospheric cutoff, for excitation from the ground state. Atomic O, N and N$^+$ have strong transitions and high abundances in the mesosphere. The product of column density and cross section for these species can be as high as $10^5$ for O and several hundred for N and N$^+$, making them potential candidates for amplified spontaneous emission. However they require vacuum-ultraviolet wavelengths for excitation.