Molecular Line Opacity of LiCl in the Mid‐Infrared Spectra of Brown Dwarfs

We present a complete line list for the X 1 Σ + electronic ground state of 7 Li 35 Cl, computed using fully quantum-mechanical techniques. This list includes transition energies and oscillator strengths in the spectral region 0.3-39,640.7 cm -1 for all allowed rovibrational transitions in absorption within the electronic ground state. The calculations were performed using an accurate hybrid potential constructed from a spectral inversion fit of experimental data and from recent multireference single- and double-excitation configuration interaction calculations. The line list was incorporated into the stellar atmosphere code PHOENIX to compute spectra for a range of young to old T dwarf models. The possibility of observing a signature of LiCl in absorption near 15.8 μm is addressed and the proposal to use this feature to estimate the total lithium elemental abundance for these cool objects is discussed.