Scientific Theme: Advanced Modeling and Observing Systems

Complementary Research: Innovative Research Program
Interdisciplinary. This study requires a synergistic approach based in chemical theory, laboratory experiments and
atmospheric science. We described in the initial stage the collaboration between theory and experiment. Once the
results are available, expertise with atmospheric aerosols, field observations regarding sunrise emissions from Arctic
ice and atmospheric modeling are necessary and available in CIRES.
Research Plan. This study chooses for illustration the molecule methane-diol, CH2(OH)2 and its hydrated form
CH2(OH)2·H2O.
CH2(OH)2 + hv → CH2O + H2O (A)
CH2(OH)2·H2O + hv → CH2O + 2H2O (B)
The dehydration reaction will be used as prototype reactions to study the vibrational overtone absorption
mechanism. We already computed the reaction paths for A and B. A very interesting result was obtained. While the
barrier to reaction was approximately 45 kcal/mol for reaction A, the reaction of the van der Waals complex (B)
takes place with a barrier of only approximately 29 kcal/mol suggesting the possibility of catalysis of reaction (A)
by water. The main focus of the theoretical research is the dynamics and kinetics of the vibrational overtone
absorption-induced chemical reactions using the method of direct dynamics.
The experimental work will involve two related studies:
A spectroscopic study of the vibrational spectrum of this molecule never before obtained. A Fourier-
Transform spectrometer available in the Vaida group will be used to obtain the mid IR spectrum. A newly
developed cavity-ring-down spectrometer will allow the investigation of high OH vibrational overtones,
which are at the barrier for reaction.
Light initiated reactions of the organic acids and alcohols will be investigated to obtain the fundamental
data base needed as input to chemical atmospheric models.
Expected Outcome and Impact. The goal of this inquiry is to acquire a valid theoretical description confirmed by
experiment of how water-catalyzed photochemical reactions occur. The outcome will be to introduce in atmospheric
models new classes of photo-processing reactions relevant to atmospheric aerosols, ices and other water-air
environmental interfaces.
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