The dissertation focuses on the temperature dependent rate coefficient measurement of reactions in the interstellar medium using a coaxial molecular beam ring electrode ion trap apparatus. The first chapter introduces the previous studies of ion-molecule reactions in the ISM, the types of instruments mainly used in the reaction rate coefficient study, the former research on the ring electrode ion trap and the gas phase reaction mechanisms. Compare to other instruments, our molecular beam - ring electrode ion trap is extremely good at ion cooling and temperature control for both ions and neutral molecules. Chapter two describes each part of the instrument used in detail. Ions produced by electron impact in the ion source chamber, are mass filtered and then reach the ring electrode ion trap. In the trap, ions collide with molecules in the molecular beam where reaction takes place. When the reaction is done, all the ions remained in the trap (the reactant and product ions) come out and move to the detector. The molecular beam terminates at residual gas analyzer which is used for the number density calibration. The third chapter shows how the temperature of ions and molecules are controlled separately in order to find the reaction mechanism. Ions are cooled by the pulsed He buffer in the ring electrode trap and a chopped beam is used to make sure the ions are cooled to the desired low temperature when the reaction takes place. Chapters four to six describe the three reactions being studied using this instrument: N₂⁺ + H₂O charge transfer reaction, H₃O⁺ + C₂H₄ proton transfer reaction and H3O⁺ + (C₂H₂)₂/C₂H₂ dimer reaction. The temperature dependent rate coefficient data of these reactions are explained by the average dipole orientation theory, statistical theory and Colussi's acetylene dimer model, respectively. Two temperatures are defined and applied in the experimental rate coefficients analysis: ion-molecule center of mass collision temperature and the reaction statistical temperature which is based on the numbers of degrees of freedom of both reactants.

abstract: It is well known that the geckos can cling to almost any surface using highly dense micro/nano fibrils found on the feet that rely on Van Der Waals forces to adhere. A few experimental and theoretical approaches have been taken to understand the adhesion mechanism of gecko feet. This work explains the building procedure of custom experimental setup to test the adhesion force over a temperature range and extends its application in space environment, potentially unsafe working condition. This study demonstrates that these adhesive capable of switching adhesive properties not only at room environment but also over a temperature range of -160 degC to 120 degC in vacuum conditions. These conditions are similar to the condition experienced by a satellite in a space orbiting around the earth. Also, this study demonstrated various detachment and specimen patch preparation methods. The custom-made experimental setup for adhesion test can measure adhesion force in temperature and pressure controlled environment over specimen size of 1 sq. inch. A cryogenic cooling system with liquid nitrogen is used to achieve -160 degC and an electric resistive heating system are used to achieve 120 degC in controlled volume. Thermal electrodes, infrared thermopile detectors are used to record temperature at sample and pressure indicator to record vacuum condition in controlled volume. Reversibility of the switching behaviour of the specimen in controlled environment confirms its application in space and very high or very low-temperature conditions. The experimental setup was developed using SolidWorks as a design tool, Ansys as simulation tool and the data acquisition utilizes LabVIEW available in the market today. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

A cryogenic (325-80 K) ion mobility-mass spectrometer was designed and constructed in order to improve the analytical figures-of-merit for the chemical analysis of small mass analytes using ion mobility-mass spectrometry. The instrument incorporates an electron ionization source, a quadrupole mass spectrometer, a uniform field drift cell spectrometer encased in a cryogenic envelope, and an orthogonal geometry time-of-flight mass spectrometer. The analytical benefits of low temperature ion mobility are discussed in terms of enhanced separation ability, ion selectivity and sensitivity. The distinction between resolving power and resolution for ion mobility is also discussed. Detailed experimental designs and rationales are provided for each instrument component. Tuning and calibration data and methods are also provided for the technique. Proof-of-concept experiments for an array of analytes including rare gases (argon, krypton, xenon), hydrocarbons (acetone, ethylene glycol, methanol), and halides (carbon tetrachloride) are provided in order to demonstrate the advantages and limitations of the instrument for obtaining analytically useful information. Trendline partitioning of small analyte ions based on chemical composition is demonstrated as a novel chemical analysis method. The utility of mobility-mass analysis for mass selected ions is also demonstrated, particularly for probing the ion chemistry which occurs in the drift tube for small mass ions. As a final demonstration of the separation abilities of the instrument, the electronic states of chromium and titanium (ground and excited) are separated with low temperature. The transition metal electronic state separations demonstrated here are at the highest resolution ever obtained for ion mobility methods. The electronic conformational mass isomers of methanol (conventional and distonic) are also partially separated at low temperature. Various drift gases (helium, neon, and argon) are explored for the methanol system in order to probe stronger ion-neutral interaction potentials and effectuate higher resolution separations of the two isomeric ions. Finally, two versatile ion source designs and a method for axially focusing ions at low pressure (1-10 torr) using electrostatic fields is presented along with some preliminary work on the ion sources.