<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>X</mml:mi><mml:mspace width="0.2em"/><mml:mmultiscripts><mml:mi>Σ</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>1</mml:mn></mml:mmultiscripts></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>a</mml:mi><mml:mspace width="0.2em"/><mml:mmultiscripts><mml:mi>Σ</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>3</mml:mn></mml:mmultiscripts></mml:mrow></mml:math>states of LiCs studied by Fourier-transform spectroscopy

We present the first high-resolution spectroscopic study of LiCs. LiCs is formed in a heat-pipe oven and studied via laser-induced fluorescence Fourier-transform spectroscopy. By exciting molecules through the $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}^{+}\text{\ensuremath{-}}B\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ and $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}^{+}\text{\ensuremath{-}}D\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ transitions vibrational levels of the $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}^{+}$ ground state have been observed up to $3\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ below the dissociation limit enabling an accurate construction of the potential. Furthermore, rovibrational levels in the $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ triplet ground state have been observed via singlet-triplet mixing in the higher excited states. With the help of coupled channels calculations, accurate singlet and triplet ground-state potentials were derived reaching the atomic ground-state asymptote. These potentials yield an accurate determination of the singlet and triplet ground-state dissociation energies and allow first predictions of cold collision properties of $\mathrm{Li}+\mathrm{Cs}$ pairs.