Research Overview

	Terahertz Spectroscopy of Ions and Clusters CW THz laser experiments are used to measure VRT spectra of both protonated and neutral water clusters as a means of precisely characterizing the nature of hydrogen bonding interactions and proton motion in liquid water.
	Synchrotron X-Ray Spectroscopy of Liquids and Liquid Surfaces Liquid microjets are used to inject volatile liquids(e.g. water) and solutions into high vacuum environments where soft X-ray spectroscopy experiments can be conducted using the Berkeley/LBNL Advanced Light Source, providing a powerful new way to probe the nature of liquids and their solutions.
	Surface Structure of Electrolyte Solutions Textbooks describe surfaces of aqueous electrolytes as being devoid of ions, thought to be repelled from the surface by image charge forces. However, our recent femtosecond SHG experiments have actually revealed ENHANCED concentrations of several ions at the water surface, in agreement with recent computer simulations. We seek to establish the mechanism and explore the chemical consequences of this ion enhancement via femtosecond nonlinear laser spectroscopy experiments.
	The Mechanism of Water Evaporation: Using liquid microjets in combination with mass spectrometry, Raman spectroscopy, and cavity enhanced Raman spectroscopy, we are assembling a detailed molecular description of how water molecules escape from the surface of the liquid.
	Infrared Laser Spectroscopy of Hydrated Ions With the Williams Group, we are exploring the structure of electrospray generated ions using spectroscopy and ion cyclotron resonance mass spectrometry.
	Computational Modeling of Liquid Water and Water Clusters New potential energy surfaces derived from our VRT spectroscopy data are used to model liquid and solid water and their surfaces.
	Femtosecond Spectroscopy of Nanostructures In collaboration with the Yang and Alivasatos groups, we are studying the properties of semiconductor nanowire and nanoribbon lasers and waveguides, tetrapods, and composite solar energy materials.
	High Spectral Resolution Femtosecond CARS Spectroscopy and Imaging By using chirped femtosecond pulses in CARS experiments, we transcend the transform limit and achieve spectral resolution >300. This permits subtle effects(e.g. various amide stretch features) to be discerned and highly specific chemical imaging of complex materials to be achieved.
	Infrared Cavity Ringdown Laser Absorption Spectroscopy Pulsed Cavity Ringdown Spectroscopy is being developed in the Saykally Lab as a simple and convenient means for measuring gaseous samples with very high sensitivity and high spectral recolution. A current goal is to develop a pulsed source of coherent IR radiation that will cover the entire spectrum, as an alternative to diode lasers, color center lasers, and FTIR spectrometers. This system will be used in studies of molecular clusters and ions that are of interest in the atmosphere and interstellar space.

Computational Code Downloads

Argon-Water Potential -- aw2.tar

Argon-Ammonia Potential -- ArNH3_IPS_Requests.zip

HCl Dimer Potential -- fort.2, pot.f