CIRES Council of Fellows>

Veronica Vaida

Ph.D., Yale University, 1977
Professor of Chemistry and Biochemistry

E-mail: vaida@spot.colorado.edu
Office: Ekeley W145F
Phone: 303-492-8605
Web: Prof. Vaida
(Dept. of Chemistry and Biochemistry)

Research Interests

Spectroscopic Studies of Atmospheric Molecules, Radicals, and Their Complexes
Professor Vaida's research interest focuses on issues of photoreactivity in the atmosphere. The approach employed to obtain the structure and dynamics of molecules, radicals, and their complexes involves a combination of spectroscopic, photofragment and theoretical techniques. Several lines of inquiry are being pursued:

1. Small predissociative molecules such as NH₃, CS₂, OCS, OClO, and O₃ are under investigation to obtain the structure and dynamics of their reactive electronic states. The experimental techniques employed for these studies are direct absorption resonance, enhanced multiphoton ionization, laser-induced fluorescence and resonance Raman of supersonically cooled samples. The experimental data are modeled theoretically using ab initio electronic structure theory as well as calculations of chemical dynamics on the reactive potential energy surfaces.

2. Reactivity in solvent environments is studied using molecular complexes. Spectroscopic perturbations produced by intermolecular interactions are analyzed to bridge the gap between gas and condensed phases. This method employs molecular beam techniques where weakly bound molecular clusters of different composition and size can be produced in a controlled fashion and investigated spectroscopically.

3. The photochemistry of weakly bound clusters involving dissociative molecules is under investigation. Efficient covalent bond chemistry is observd to compete with energy flow to the weaker van der Waals bonds in molecular dimers containing highly dissociative samples.

4. The problematic thrust of the group is the investigation of photo-reactive molecules and clusters important in atmospheric chemistry. A recent example is the group's quantitative laboratory study of light-induced reactions important in the stratosphere. In collaboration with Dr. Susan Solomon from the Aeronomy Laboratory at NOAA [ About this Lab ] in Boulder, who has measured the concentration of chlorine dioxide over Antarctica, Professor Vaida's lab proposes, on the basis of its laboratory results, a new chemical reaction that contributes to polar ozone depletion. In parallel, a program to evaluate the photoreactivity of bimolecular complexes formed by molecules or radicals in the atmosphere is being developed. This work aims to obtain a laboratory data base needed for inclusion of the photochemistry or bimolecular complexes in atmospheric models.

Awards and Prizes

Fellow of the Alfred P. Sloan Foundation, 1981-83
Camille and Henrey Dreyfus Teacher-Scholar Award

Selected Publications

• L.A. Brown and V. Vaida, "The Photoreactivity of the Oxygen Dimer," J. Phys. Chem. 100, 7849 (1996).
• L.A. Brown, V. Vaida, D.R. Handson, J.D. Graham, and J.T. Roberts. "The Uptake of Chlorine Dioxide by Model PSC's Under Stratospheric Conditions," J. Phys. Chem. 100, 3121 (1996).
• J.D. Graham, J.T. Roberts, L. Brown, and V. Vaida. "The Uptake of Chlorine Dioxide by Model Polar Stratospheric Cloud Surfaces: Ultrahigh Vacuum Studies," J. Phys. Chem. 100, 3115 (1996).
• G.J. Frost, L.M. Goss, and V. Vaida. "High Resolution UV-VIS Absorption Cross Sections of OClO at Stratospheric Temperatures," J. Geophys. Res. 101, 3879 (1996).
• G.J. Frost, L.M. Goss, and V. Vaida. "High Resolution UV-VIS Absorption Cross Sections of NO₂ at Stratospheric Temperatures," J. Geophys. Res. 101, 3869 (1996).

Vaida is also one of the CIRES Faculty who teach at the University of Colorado at Boulder with teaching loads equivalent to those of CU faculty rostered solely in departments and programs.