Aerosol spectroscopy of dihydroxyacetone: Gas phase and nanoparticles

Dihydroxyacetone aerosols with particle diameters around 50 nm were produced in an electrospray at ambient temperature and pressure. The vibrational spectra of the aerosols between 800 and 4000 cm(-1) were recorded with a Fourier transform infrared spectrometer. Depending on the experimental conditions, an appreciable amount of gas-phase 1,3-dihydroxy-2-propanone appeared in the infrared spectra of the particulate phase. In contrast to the gas phase, the particulate phase was found to consist of the chemically bound dimer 2,5-dihydroxymethyl-2,5-dihydroxy-1,4-dioxane. Temperature-dependent gas-phase spectra of dihydroxyacetone monomer between 310 and 440 K reveal interesting torsional dynamics, which are analyzed with the help of a detailed four-dimensional model. Experimental spectra of the nanoparticles were simulated using a Kramers-Heisenberg dielectric function. The comparison with ab initio calculations of the free molecule and small clusters leads to a first microscopic picture of the intermolecular interactions in the condensed phase.