  Line lists for magnesium oxide are computed and extensive comparisons are
made with existing experimental spectra. The LiTY line lists cover all
ro-vibration transitions within the five lowest-lying electronic states
($X\,{}^1\Sigma^+$, $a\,{}^3\Pi$, $A\,{}^1\Pi$, $B\,{}^1\Sigma^+$ and
$b\,{}^3\Sigma^{+}$) and five isotopologues: $^{24}$Mg$^{16}$O,
$^{25}$Mg$^{16}$O, $^{26}$Mg$^{16}$O, $^{24}$Mg$^{17}$O, $^{24}$Mg$^{18}$O,
$^{24}$Mg$^{17}$O and $^{24}$Mg$^{18}$O. The calculation use potential energy
cures, spin-orbit and electronic angular momentum couplings curves determined
by fitting to empirical energy levels; these levels are reproduced to within
0.01 \cm\ in most cases. Computed nuclear-motion wavefunctions are combined
with {\it ab initio} dipole moment curves to give transition intensities and
excited state radiative lifetimes which are compared with laboraroty
measurements. The $^{24}$Mg$^{16}$O line list comprises 186 842 ($J\le 320$)
ro-vibronic states and 72 833 173 transitions with angular momenta, $J$, up to
300 and covering wavenumbers up to 33 000 cm$^{-1}$ ($\lambda > 0.3$ $\mu$m).
The line lists are suitable for temperatures up to about 5000 K. They are
relevant to astrophysical studies of exoplanet atmospheres, cool stars and
brown dwarfs, and are made available in electronic form at the CDS and ExoMol
databases.
