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Mark Sulkes, Professor
Ph.D., 1978, Cornell
Office: 5067 Percival Stern Building
Telephone: (504) 862-3587
Email: cm06acf@tulane.edu
Discipline:
Physical Chemistry
Areas of current interest include:
We employ laser spectroscopic techniques to study chemically interesting species in cold molecular beams. Lately, work has centered on highly reactive organosilicon intermediates, particularly silylenes, silyl radicals, and their possible reaction products with selected reactants. Reactive organosilicon species can be produced in the molecular beam from stable precursors using UV laser photolysis, high voltage discharges, or flash pyrolysis. Another novel and particularly promising approach has been via laser ablation of strained ring precursors. After the production of reactive species, we employ the mass measurement capability inherent in time of flight molecular beams to identify products formed as a function of mass. More detailed, information on species produced can be obtained from ZEKE or REMPI spectroscopic approaches. A particularly exciting aspect of this work is the possibility of carrying out and observing novel chemistry in the “preparative chemistry zone”, before the molecular beam is formed, and then using beam techniques to assess the results. Such a preparation/analysis approach can have practical applications that still have been little exploited. For example, high voltage discharge has been used to treat and remove volatile organic compounds (VOC’s) from air or exhaust. Generally the initial intermediates produced and their subsequent chemistry are not known. High voltage discharge on selected VOC’s followed by molecular beam analysis can generally provide information of this kind, allowing for the use of fundamental chemical data to design better future remediation apparatus.
The foregoing studies are mainly of neutral species. Charged species can also be studied. The time of flight system employs reflectron grids for better mass resolution. It is possible to mass select desired ions before the reflectron, subject them to laser photolysis pulses in the reflector region, and then mass analyze the resulting ionic fragments by time of flight. Tandem mass selectivity allows molecular beam experiments to be done that complement the experiments done in flow tube tandem mass spectrometry experiments.
Sometimes it is possible to study expansion cooled species by light-based techniques (fluorescence excitation, fluorescence lifetimes, absorbance). We have a separate apparatus well implemented for these possibilities.
Selected Publications
R. Subramanian, M. Sulkes, "Production of a slit skimmer for use in cold supersonic molecular beams"
Review of Scientific Instruments, 79 (1), art. no. 016101 (2008).
I. Borthwick, L. Baldwin, M. Sulkes, M. Fink, “Molecular Beam Photochemistry of Some Organosilanes and Organopolygermanes”, Organometallics 19, 139 (2000).
M. Sulkes, L. C. Baldwin, M. J. Fink, “Molecular Beam Study of Possible CVD Intermediates from Group-14 Organometallic Precursors”, Chem. Phys. Lett. 318, 448 (2000).
I. Borthwick, M. Sulkes, M. Fink, “Gas Phase Photolytic Production of Si2N from Azidotrimethylsilane,” Main Group Metal Chemistry 23, 203 (2000).
M. Sulkes, M.J. Fink, S. E. Gottschling and K. M. Baines, “Laser Ablation of Hexamesitylcyclotrigermane and Hexamesitylcyclosiladigermane in a Molecular Beam”, Organometallics 21, 2138 (2002).
M. Sulkes and M. J. Fink, “Laser Ablation of Ring Strained Precursor Molecules: Selective Product Fragment Generation”, Chem. Phys. Lett. 379, 60 (2003).
M. Sulkes, “Selective Bond Fragmentation in Pulsed Laser Ablation of Ring Strained Compounds: Evidence for a Thermal Mechanism”, Chem. Phys. Lett. 402, 165 (2005).
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