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Title Non-thermal processes on ice and liquid micro-jet surfaces
URL
Publication Date
Date Accessioned
Degree PhD
Discipline/Department Chemistry and Biochemistry
Degree Level doctoral
University/Publisher Georgia Tech
Abstract Processes at the air-water/ice interface are known to play a very important role in the release of reactive halogen species with atmospheric aerosols serving as catalysts. The ability to make different types of ice with various morphologies, hence, different adsorption and surface properties in vacuum, provide a useful way to probe the catalytic effect of ice in atmospheric reactions. Also, the use of the liquid jet technique provides the rare opportunity to probe liquid samples at the interface; hitherto impossible to investigate with traditional surface science techniques. Studies of reactions on both ice and liquid surfaces at ambient conditions are usually complicated by the rapid desorption and adsorption processes due to the high evaporation rates at the surface. To gain a better understanding and improve modeling of several atmospheric relevant reactions, it is therefore important to develop laboratory techniques that provide an opportunity to investigate non-thermal reactions on both ice and liquid surfaces. Detailed investigation of the interactions of atmospheric relevant molecules (methyl iodide and hydrogen chloride) on water ice at low temperature in UHV conditions has been carried out. These interactions were studied using different techniques such as temperature programmed desorption (TPD), electron stimulated desorption (ESD) and resonance enhanced multiphoton ionization (REMPI). Unlike probing reactions on ice surfaces, investigating air/liquid interfaces present several challenges. This is because traditional surface science techniques require an ultra high vacuum environment to prevent distortion of information due to interference from equilibrium vapor above the liquid surface during data acquisition. The liquid jet technique facilitates the direct study of continually renewed liquid surfaces in high vacuum, thereby preventing the constant changing of the properties and composition of the liquid surface due to the aging process (diffusion of impurities or liquid constituent). A linear time-of-flight mass spectrometer has been used to monitor ion ejection during laser irradiation of liquid jet containing aqueous solutions and pure water. Since these ions are ejected exclusively from the surface of the liquid and the cluster distributions observed are influenced by the local structure, these experiments provide a sensitive probe of the liquid vacuum interface of these solutions. Though the research is fundamental, the results obtained from these investigations indicate how the discontinuity of bulk properties on the surface of both ice and aqueous solutions affects interfacial reactions.
Subjects/Keywords Resonance enhanced multiphoton ionization (REMPI); Liquid jet; Coulomb repulsion; Low temperature ice; Ice; Atmospheric chemistry; Jets Fluid dynamics.; Atmospheric aerosols; Halides; Photoionization
Contributors Orlando, Thomas (Committee Chair); Bottomley, Lawrence (Committee Member); Fernandez, Facundo (Committee Member); Huey, Greg (Committee Member); Wine, Paul (Committee Member)
Country of Publication us
Record ID handle:1853/39475
Repository gatech
Date Indexed 2018-01-11
Issued Date 2011-01-19 00:00:00
Note [degree] Ph.D.; [advisor] Committee Chair: Orlando, Thomas; Committee Member: Bottomley, Lawrence; Committee Member: Fernandez, Facundo; Committee Member: Huey, Greg; Committee Member: Wine, Paul;

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…mass spectrometer (ToF-MS) for neutral atomic and molecular fragment detection using resonance enhanced multiphoton ionization (REMPI). The system is also equipped with and a quadrupole mass spectrometer (QMS) to analyze…

…LIST OF TABLES 2.1 5.1 Effective temperature of Maxwell Boltzmann distribution with corresponding translational kinetic energy. . . . . . . . . . . . . . . . . . . 17 Second ionization potentials of alkaline-earth metal. . . . . . . . . . . 75…

…spectrometer experimental setup with the pulse sequence of both the desorption and ionization (REMPI) laser. This setup was used to detect neutral iodine atoms released during the photodissociation of adsorbed methyl iodide on ice. 8 Temperature…

…x5D; A critical unknown factor in these reactions is the extent of ionization of HCl molecules adsorbed on PSC. Kang et al. used reactive ion scattering (RIS) and low energy secondary ion mass spectrometry (SIMS) to measure the…

…extent of ionization as a function of temperature and found mostly molecular HCl at temperatures below 70 K, a mixture of the ionized and molecular forms of HCl from 90–120 K, and complete ionization above 140 K.[23] Molecular beam experiments…

…studies shows evidence of complete ionization at 80 K on ice films,[29, 30] while others report molecular bands that exist up to 125 K.[31] In addition, the kinetics and rate of adsorption of HCl on ice have been investigated as…

…39-41] have been use to investigate liquids in an ultrahigh vacuum environment. The liquid jet technique is also valuable for laser ionization of liquid surfaces in vacuum, and has been employed to examine the gas-liquid interface of organic…

…solutions. [42-45] Monitoring ejected ions from UV laser ionization of liquid jets with time of flight mass spectrometry was pioneered by Kondow and co-workers.[44] However, this body of work was done exclusively on solutions of…

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