Knowledge Bank

Initial results of a study of the infrared spectra of gaseous alkali metaborates are reported. Mass spectrometry shows the saturated vapors of these compounds to consist of monomer and dimer molecules and indicates for the latter the structure [ \begin{array}{lllll} &M\ O=B-O&&O-B=O&&M=Li, Na, \ldots Cs\ &M \end{array} ] The absorption spectrum of sodium metaborate vapor shows bands at 1930, 1450, 1235, 1060 and $600cm-1$. The 1930 $cm-1$ band has been assigned as the B = O bond stretching frequency in both monomer and dimer. It is found essentially unshifted in the spectrum of cesium metaborate vapor, but is shifted to $1965cm-1$ in the spectrum of $B10$-enriched sodim metaborate vapor. The assignment of the lower-frequency bands will also be discussed.