Understanding of photophysics and chemical dynamics in condensed media is the major thrust of our research. These studies invariably involve laser- based spectroscopic techniques that are implemented in both frequency and time domain, over the spectral range from far infrared to the deep ultraviolet.

Characterization of molecular monolayers at metal surfaces by polarization- modulation FTIR reflection absorption spectroscopy (PM-FTIRRAS) and optical second harmonic generation (SHG) measurements of orientation, organization, and electron transfer processes at liquid/liquid electrochemical interfaces.

We are exploiting new experimental techniques such as ultrafast multidimensional multicolor IR spectroscopy that are vibrational analogues of multidimensional NMR. The extension beyond a single dimension gives these techniques the ability to disentangle structural information from complex spectra where the couplings, correlations, and relative angular orientations between structural units are revealed as "cross peaks".

Vibrational spectroscopy is among the main tools of physical chemistry in the exploration of molecular properties. Interpretation of the experiments requires theoretical calculations of the spectra, and for large, non-rigid molecules this is a formidable challenge. An algorithm developed in our group in recent years, the Vibrational Self-Consistent Field (VSCF) method(1), led to major progress on this problem, and has emerged as a leading tool in this field.

The aim of research in my group is to understand and exploit colloidal interactions, chemistry, assembly, and response to external fields to design microstructured materials with enhanced functionality for composites, biomimetic applications, alternative energy, and environmental remediation. Current projects involve both fundamental and applied elements of colloid synthesis and surface modification, microfluidics, guided- and self-assembly, and characterization of structure and dynamics by quantitative confocal microscopy and light scattering.

My interests focus on the modeling of ultrafast dynamics and relaxation processes of large molecules, biological complexes and semiconductors and how they can be probed by novel optical spectroscopic techniques. My group works on developing coherent optical and infrared pulse sequences which accomplish goals analogous to multidimensional NMR and have the capacity to probe protein structures and dynamics with high temporal, spectral, and spatial resolution.

We are interested in the mechanisms of photochemical interactions between the solar radiation and atmospheric aerosol particles. Can aerosol particles serve as efficient catalysts of photochemical processes? What sort of chemistry happens inside these particles as they drift through the atmosphere exposed to solar radiation? Can photochemical reactions on particle surfaces make the particles more toxic? In our laboratory, we try to find answers to these intriguing problems using modern analytical techniques based on laser spectroscopy, chromatography, and mass- spectrometry.

We employ multimodal nonlinear microscopy tools (CARS/SHG/TPEF) to quantitatively image biological tissues and structures. We are also interested in characterizing the nonlinear optical properties of nanostructures. The third order optical response of nano-compounds is explored by detecting the coherent anti-Stokes electronic signatures of such systems. We use focus-engineered CARS techniques to improve contrast in nonlinear microscopy.