Matrix Isolation of High-Temperature Vapors: Boric Oxide

Abstract

The matrix isolation technique has been extended to allow molecules which are in equilibrium with solids at high temperatures to be trapped and studied at low temperatures. A beam of the hot vapor issuing from a Knudsen cell or a heated surface is premixed with a large excess of argon or xenon just prior to condensation at 20°K. The method was applied to boric oxide vapor which was vaporized from the liquid at 1400°K. The infrared absorption spectrum of the B2O3 molecule in a solid inert gas matrix was measured between 280 and 3600 cm−1 and compared with the known vapor emission spectrum. Several new bands were found near 500 cm−1 which led to a considerable alteration in the vibrational assignment and the thermodynamic properties of the gaseous molecule. The infrared spectrum of B2O2 (produced by heating boron plus boric oxide) isolated in a matrix yielded one absorption band which agreed with the emission spectrum. An extensive normal coordinate treatment of B2O3 was made utilizing the observed spectra of the B10 and B11 substituted molecules.