No abstract

No abstract

New infrared spectra of pure bulk molecular sulfuric acid and its mono-and tetrahydrates under equilibrium water partial pressure conditions have been obtained using an internal reflection geometry. For each of the species present (H 2 SO 4 , HSO 4and SO 4 2-), a well-defined set of core SO 4 vibrations has been identified and assigned to individual vibrational modes. Using these data, earlier literature data has been reexamined. Existing methods for the quantification of composition and ion speciation in H 2 SO 4 /H 2 O mixtures are examined and the need for a more sophisticated method for the determination of sulfate aerosol composition is proposed.

The interaction of SO(3) and H(2)O at low temperatures upon an inert surface has been studied with infrared spectroscopy and compared to the predictions of recent computational studies. At low temperatures and low water partial pressures, amorphous deposits of molecular H(2)SO(4) complexed with variable amounts of H(2)O in a ratio of between 1:1 and 2:1 are formed. Upon annealing, this material ejects water and converts first to a 1:1 H(2)SO(4).H(2)O complex and subsequently to anhydrous H(2)SO(4). Adding water to the amorphous molecular hydrate results in the formation of a new species, which on the basis of its thermal behavior and by comparison to theoretical predictions can be attributed to a molecular polymer with a repeat unit of (H(2)SO(4).(H(2)O)(2))(n)(). Implications of these observations for the initial stages of the formation of sulfate aerosol in the atmosphere and their surface reactivity are discussed.