Following the Lithium: Tracing Li-bearing Molecules Across Age, Mass, and Gravity in Brown Dwarfs
Ehsan Gharib-Nezhad, Mark S. Marley, Natasha E. Batalha, Channon, Visscher, Richard S. Freedman, Roxana E. Lupu

TL;DR
This study models the atmospheric chemistry and spectra of lithium-bearing molecules in brown dwarfs to improve detection methods for understanding their mass and age, especially in cooler atmospheres where atomic lithium is absent.
Contribution
It provides the first comprehensive modeling of molecular lithium signatures in brown dwarf atmospheres using updated opacity data and thermochemical calculations.
Findings
LiF at 10.5-12.5 microns is a strong spectral signature.
LiCl at 14.5-18.5 microns is detectable.
LiH shows a narrow feature at 9.38 microns.
Abstract
Lithium is an important element for the understanding of ultracool dwarfs because it is lost to fusion at masses above . Hence, the presence or absence of atomic Li has served as an indicator of the nearby H-burning boundary at about between brown-dwarfs and very low-mass stars. Historically the "Lithium test", a search for the presence and strength of the Li line at 670.8 nm, has been a marker if an object has a substellar mass with stellar-like spectral energy distribution (e.g., a late-type M dwarf). While the Li test could in principle also be used to distinguish masses of later-type L-T dwarfs, Li is predominantly no longer found as an atomic gas, but rather a molecular species such as LiH, LiF, LiOH, and LiCl in their cooler atmospheres. L- and T-type brown dwarfs are also quite faint at 670 nm and thus challenging targets for high resolution…
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