PNNL

Abstract

Glyoxal, methylglyoxal and 2,3-butanedione (diacetyl) are all known biomass burning effluents and suspected aerosol precursors. Pressure-broadened quantitative infrared spectra of glyoxal, methylglyoxal and diacetyl vapors covering the 520–6500 cm-1 range are reported at 0.11 cm-1 resolution, each with a composite spectrum derived from a minimum of ten different sample pressures for the compound, representing some of the first quantitative data for these analytes. The ordinate corresponds to a 1 meter optical pathlength and a mixing ratio of 1ppmv at 296 K. Many vibrational assignments for methylglyoxal are reported for the first time, as are some near-IR and far-IR bands of glyoxal and diacetyl. To complete the vibrational assignments, the quantitative far-infrared spectra (25 to 600 cm-1) of all three vapors are also reported, methylglyoxal for the first time. Density functional theory and ab initio MP2 theory are used to help assign vibrational modes. Potential bands useful for atmospheric monitoring are discussed.