7626

7098

كارشناسي ارشد

شيمي فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده شيمي

1391

چهارده،98ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمود تبريزچي، حسين فرخ پور

حسن قاضي عسگر

20/1/92

عزت كشاورزي، مهدي رنجبر

شيمي

ID7098

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Mass Calibration of Laser Ionization Time of Flight Mass Spectrometer Using Alkali Salts Hajar Azad h azad @yahoo com Department of Chemistry Isfahan University of Technology Isfahan Iran Degree M Sc Language FarsiMahmoud Tabrizchi m tabriz@cc iut ac ir Hossein Farrokhpour h farrokh@cc iut ac ir Abstract Time of Flight TOF mass spectrometry is one of the most important methods foranalysis of materials In this method the ions produced by an ionization source areaccelerated in a uniform electric field and then separated in a field free region based ontheir mass to charge ratio and thus will arrive to detector at different times Any massspectrometer requires mass calibration to determine accurate mass of unknown species Usually standard masses are used for accurate calibration In this thesis the TOF massspectrometer design and constructed in the department of chemistry was calibrated usingalkali salts as standard substances In this work an Nd YAG laser at third harmonic nm with ns pulses was used as a desorption ionization source Irradiation of high power laser on a solid surface caused rapid melting and vaporization of the materialsfollowed by atomization excitation and ionization Thin aluminum foil was used as asupport to hold the sample in the ionization region The support was mounted as a repellerin the accelerator The support was made in contact with aqueous solutions of alkali halides M After drying the sample and closing the vacuum chamber vacuum was establishedusing two rotary and two turbo molecular pumps Ultimate vacuum of mbar wasachieved Laser was then aligned to irradiate the sample through a quartz window Thelaser beam was focused to enhance evaporation and ionization of the sample Time offlight spectra of individual alkali halides including LiCl NaCl KCl RbCl CsCl wererecorded Approximate masses were calculated from the m z eUT D where U is theapplied voltage to the accelerator and T and D are the flight time and length respectively It was found that all alkali halides produce ions of M and M MX n type where n M the alkali atom in the salt and X is its counter halide ion Taking accurate masses ofthe known ions a calibration curve was obtained by plotting m versus flight time usingm aT b Using this calibration curve Al ion is also identified Binary and ternarymixtures of alkali salts were also used to obtain more accurate mass calibration For moreaccurate calibration a mixture of all alkali chlorides were used By this a broad range offlight times were covered by different ions An average mass accuracy of wasobtained

محمود تبريزچي، حسين فرخ پور

حسن قاضي عسگر

عزت كشاورزي، مهدي رنجبر