Knowledge Bank

The pure rotational spectra of LiSH ($X~1A\prime )$ and two of its isotopomers ($\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$LiSH, LiSD) were recorded using millimeter/submillimeter-wave direct absorption techniques. The molecule was produced by reacting lithium vapor with $H2S$ in the presence of a d.c. discharge. Transition ranging from $J=1\to 2$ to $J=13\to 14$, spanning the region of 73-520 GHz, were measured for $\mathrm{<mrow\; data-mjx-texclass="ORD">7</mrow>}$LiSH, as well as 3-4 transitions for the $\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$Li and deuterium isotopomers. The spectra showed an extensive $Ka$ ladder structure for the three species, which is consistent with the molecule being an asymmetric top. Rotational constants for all three molecules have been determined, as well as $r0$ and $rm\mathrm{<mrow\; data-mjx-texclass="ORD">(1)</mrow>}$ structures for LiSH. This study shows that this molecule is bent, with $\Theta =93\circ$ and therefore is significantly different from the quasilinear LiOH. This structural change likely results from more covalent bonding in LiSH.