Infrared Absorption Spectra of B2O3, B2O2, and BO2 in Solid Argon Matrices

The infrared absorption spectra of B2O3, B2O2, and BO2 isolated in solid argon matrices have been investigated in the region 350–4000 cm—1. The visible absorption spectrum of matrix-isolated BO2 was observed in the region 4000–5500 Å. The gaseous species were generated in a high-temperature effusion cell and trapped under conditions of moderate to high dilution in solid argon matrices at approximately 4°K. Bands were found at 1955, 1921, 1899, 1323, and 1276 cm—1 in the infrared spectra of B210O2, B10B11O2, B211O2, and B10O2, and B11O2, respectively. For both B210O3 and B211O3 infrared spectra of the most dilute matrices show seven distinct bands in the region 450–2100 cm—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 that determined by electron diffraction, and the correlation of the normal vibrations and selection rules with those for the linear symmetric (D∞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): B210O3: 2128(A1),733(A1),536(A1);[172](A1),or [260](A1);[476](A2) 2128(B1),1242(B1),471(B1);493(B2);B211O3: 2060(A1),729(A1),518(A1),[172](A1), or [259](A1);[456](A2),2060(B1),1239(B1),454(B1);477(B2);where the bracketed frequencies were not observed directly. Thermal functions have been computed for B2O3 and compared with the available calorimetric 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.