Knowledge Bank

The infrared absorption spectra of $B2O3,B2O2$, and $BO2$ isolated in solid argon matrices have been investigated in the region $350-4000cm-1$. The visible absorption spectrum of matrix isolated $BO2$ was also observed in the region $4000-5500\backslash AA$. The molecules were generated in a high-temperature effusion cell and trapped under conditions of moderate to high dilution in solid argon matrices at approximately $4\circ K$. Bands were found at 1955, 1921, 1899, 1323, and $1276cm-1$ in the spectra of $B210O2,B10B11O2,B211O2$ and $B10O2$, and $B11O2$, respectively. For both $B210O3$ and $B211O3$ spectra of the most dilute matrices show seven distinct bands in the region $450-2100cm-1$. Six of these can be readily assigned as fundamentals and their relative intensities explained if the ''known V'' structure of $B2O3$ is supposed to have a larger apex angle than the reported, and the correlation of the normal vibrations and selection rules with those for the linear $D\infty h$ model is considered. With additional help from the measured $B10-B11$ isotope shifts and force constant calculations the following complete assignment was obtained (all frequencies in $cm-1$):$$\begin{array}{ll} B_{2}{^{10}}O_{3}:& 2128, 733(a_{1}), 536(a_{1}), 260; 480, 2128(b_{1}), 1242(b_{1}), 471(b_{1}); 493(b_{2})\ B_{2}{^{11}}O_{3}:& 2060, 729(a_{1}), 518(a_{1}), 258; 460, 2060(b_{1}), 1239(b_{1}), 454(b_{1}); 477(b_{2})\end{array}$$ where the bracketed frequencies were not observed directly. Thermal functions have been computed for $B2O3$ and compared with the available calormetric data Structural parameters and a complete vibrational assignment have been estimated for $B2O2$. The infrared and green bands observed for $BO2$ are in agreement with the high-resolution results of Johns. Thermal functions for $B2O2$ and $BO2$ have also been computed.