Zhaohui ‘Aleck’ Wang

Learn More
At the level of individual molecules, familiar concepts of heat transport no longer apply. When large amounts of heat are transported through a molecule, a crucial process in molecular electronic devices, energy is carried by discrete molecular vibrational excitations. We studied heat transport through self-assembled monolayers of long-chain hydrocarbon(More)
Ultrafast nonlinear vibrational spectroscopy with mid-IR pumping and incoherent anti-Stokes Raman probing is used to study V ) 1 excitations of OH stretching (νOH) of water and of HOD in D2O solvent (HOD/D2O). The parent νOH decay and the appearance of daughter stretching and bending excitations are simultaneously monitored, which allows for(More)
Ultrafast spectroscopy was used to study vibrational energy transfer between vibrational reporter groups on different parts of a molecule in a liquid. When OH stretching vibrations of different alcohols were excited by mid-infrared laser pulses, vibrational energy was observed to move through intervening CH2 or CH groups, taking steps up and down in energy,(More)
In a suspension of reverse micelles, in which the surfactant sodium dioctyl sulfosuccinate (AOT) separates a water nanodroplet from a bulk nonpolar CCl4 phase, ultrafast vibrational spectroscopy was used to study vibrational energy transfer from the nanodroplet through the AOT interfacial monolayer to the surrounding CCl4. Most of the vibrational energy(More)
An ultrafast flash-thermal conductance technique is used to study energy transfer from a flash-heated polycrystalline Au(111) surface to adsorbed thiolate self-assembled monolayers (SAMs). The focus is on understanding energy transfer processes to parts of SAM molecules situated within a few carbon atoms of the Au surface, by probing specific SAM functional(More)
It is difficult to study molecules at surfaces or interfaces because the total number of molecules is small, and this is especially problematic in studies of interfacial molecular dynamics with high time resolution. Vibrational sum-frequency generation (SFG) spectroscopy, where infrared (IR) and visible pulses are combined at an interface, has emerged as a(More)
We report on the energetics of intercalation of lithium, sodium and potassium in graphite by density functional theory using recently developed van der Waals (vdW) density functionals. First stage intercalation compounds are well described by conventional functionals like GGA, but van der Waals functionals are crucial for higher stage intercalation(More)
We have shown that it is possible to input heat to one location of a molecule and simultaneously measure its arrival in real time at two other locations, using an ultrafast flash-thermal conductance technique. A femtosecond laser pulse heats an Au layer to approximately 800 degrees C, while vibrational sum-frequency generation spectroscopy (SFG) monitors(More)
We have observed long-lived OH-stretch (nu(OH)) excitations (v = 1) in water during ultrafast laser ablation by a mid-infrared pulse tuned to the nu(OH) absorption maximum. The spectrum of excitations is measured using incoherent anti-Stokes Raman spectroscopy. Relative to the equilibrium water spectrum, these excitations evidence a narrowed (100 cm(-1)(More)
High-resolution underway measurements of surface water pH, CO2 fugacity (fCO2), and total dissolved inorganic carbon (DIC), along with discrete bottle sample analyses from depths, were obtained in July 2005 and September 2006 in the Mississippi River Plume (MRP) and the Orinoco River Plume (MRP). The resulting data were analyzed to compare and contrast the(More)