Ph.D. Yale University, 1977
Professor of Chemistry and Biochemistry
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:
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.
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.
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.
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.
Current Research: Light- and Water-Mediated Chemistry in the Earth’s Atmosphere
The Sun is the ubiquitous energy source for chemistry on Earth as well as for determining the planetís temperature and climate. My experimental program has proposed and investigated new sunlight-initiated chemical reactions, which occur very fast and sequester the energy from solar radiation into highenergy chemical bonds. Especially challenging to understand are processes occurring in water environments, such as the surface of water and of aqueous atmospheric aerosols, yet recent experimental and theoretical results from my research group and our colleagues point to significant changes in chemistry in the presence of water. Photochemical reaction mechanisms depend on phase and environment. Fundamental chemical processes in aqueous environments, at the water-air interface and in/on aqueous aerosols are investigated to explore the differences of chemistry in such environments. The fundamental results obtained are necessary for inclusion in atmospheric models of aerosol processes.
This work derives its intellectual merit from its fundamental molecular approach and its broader impact from the widely acknowledged importance of organic species, water, and aerosols for climate and global change.
To bring this research to a broader community, I included environmental chemistry topics in teaching chemistry at all levels. Simultaneously, I developed and delivered lectures to public and academic audiences nationwide during my tenure as Sigma Xi Distinguished Lecturer. I developed research collaborations and student exchanges abroad, specifically in New Zealand (University of Otago, Dunedin), Canada (University of Toronto), and Romania (University Babes-Bolyai).
Honors and Awards
Fellow of the Alfred P. Sloan Foundation, 1981-83
Camille and Henrey Dreyfus Teacher-Scholar Award
Dr. Vaida is a professor at the University of Colorado at Boulder.