Pulsed Laser Photolysis/Mass SpectrometryResearch Interests
The kinetics and mechanisms of homogeneous and heterogeneous chemical processes of basic and applied importance have been investigated with modern experimental and theoretical techniques.
Experimental Studies:
Two areas of research are of current interest: Kinetics of gas-phase reactions and Gas-surface reactions directly relevant to thin-film deposition.
In the first area, gas phase chemical reactions involving atoms or molecules of known vibronic states are being studied under varying experimental conditions and using different laser diagnostic techniques as Pulsed Laser Photolysis/Mass Spectrometry (PLP/MS), Pulsed Laser Photolysis/Resonance Enhanced Multi PhotonIonization/Mass Spectrometry (PLP/REMPI/MS), Pulsed Laser Photolysis/Vacuum-UV/TOF-Mass Spectrometry (PLP/VUV/TOF-MS), Cavity Ring-down Spectrometry (CRD), Pyrolysis/FTIR Spectrometry (P/FTIR), Time-resolved FTIR spectrometry (t-FTIR). Our emphasis has been placed on the elucidation of the mechanism of incipient soot formation reactions involving small unsaturated free radicals (such as C2H3, C3H3, C5H5, C6H5, and C6H5O) whose kinetic data are still scarse due to the absence of reliable diagnostic methods. Our recent development of the cavity ringdown kinetic-spectrometry technique for detection of some of these radicals allows us to determine for the first time the much needed absolute rate constants for C6H5 and C6H5O reactions.
Similar to these hydrocarbon free radicals, the kinetics of NH and NH2 reactions with NOx are relevant to the N-chemistry in fossil fuel combustion. They are also critical to the combustion of a new class of "green" propellants such as ADN (ammonium dinitramide), a potential alternative to AP (ammonium perchlorate) which is destructive to our protective O3 layer. Extensive experimental and theoretical studies on the H/N/O-chemistry have been carried out recently in our group.
On the studies of gas-surface reactions, emphasis has been placed on the deposition of III/V-nitrides and a new class of superhard materials such as SiCNx and its analogs by OMCVD (organometalic chemical vapor deposition) under low-pressure conditions. A variety of surface diagnostic methods including X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), UV photoelectron spectroscopy (UPS) and high-resolution electron energy loss spectrometry (HREELS) are available for the analysis of deposited films.
Theoretical Studies:
High-level ab initio molecular orbital methods are employed to elucidate chemical reaction mechanisms involved in the aforementioned gas-phase and gas-surface processes using the computers and advanced softwares available at the Emerson Center for Scientific Computation. In addition, two clusters of Pentium-II dual processors are available in our group for parallel calculation of large chemical systems, which cannot be carried out otherwise. These P-II cluster systems are pivotal to our studies of the decomposition of large propellants and gas-solid reactions, which often involve 15-20 heavy atoms.
For the detailed information click the one of the following links.
Group's Research Interest
and Facilities:
Pulsed Laser Photolysis/Mass Spectrometry
Time-resolved FTIR spectrometry
This page is maintained by Joonbum Park and last updated on Dec. 1997. Any comment or suggestion? Mail to jpark05@emory.edu.
