Knowledge Bank

We have observed the far infrared spectra of monomeric $GaBr3$, $GaCl3$ and $GaI3$ isolated in solid argon. We observed $\nu 2$($A2\prime \prime$), $\nu 3$(E) and $\nu 4$(E) for the chloride and bromide, but only $\nu 3$ for $Gal3$. Isotope shifts due to Ga and/or halide Isotopes were observed for each molecule, confirming the assignment. These molecules provide a clear example of the isotope shifts of the degenerate stretch, $\nu 3$. No absorption attributable to v1($A1\prime$) was observed. This is consistent with planar $D3h$ structures for each of these molecules. The structure of these halides is consistent with a model we previously proposed for $AlCl3$, a $C3v$ molecule. We also observed the spectra of the dimers $Ga2Cl6$, $Ga2Br6$, and $Ga2I6$ in solid argon.