DOCSLIB.ORG

Mass Spectrometry (MS)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Mass Spectrometry (MS) Mass Spectrometry (MS) • Technique for studying the masses of atoms or molecules or fragments of molecules • Provides information about … o Elemental composition o Molecular structure o Composition of complex mixtures o Structure & composition of solid surfaces o Isotopic ratios of atoms • Discriminate between 79Br & 81Br Mass Spectrometry Applications Skoog, Table 20-5 Mass Spectrometry Beginnings • Aston (Cambridge) o 1919 – Discovered two isotopes of neon (20Ne & 22Ne) • 1922 – Nobel Prize in Chemistry Francis William Aston o “for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole-number rule" • Discovered 212 of 281 naturally occurring isotopes www.nobel.se Obtaining a Mass Spectrum • Gaseous molecules desorbed from condensed phases are ionized • Ions are accelerated by an electric field • Ion separation by mass-to-charge ratio (m/z) ethyl benzene Skoog, Fig. 20-1 The Instrument • Sample ionization o Gas-phase o Desorption • Mass analyzer ~ monochromator o Quadrupole (Q) o Time-of-flight (TOF) o Double-focusing (B, E) o Ion trap • Ion transducer o Electron multiplier o Faraday cup Skoog, Fig. 11-1 Ion Transducers • Electron multiplier o Analogous to a photomultiplier tube (PMT) o Rugged & reliable o Current gain ~ 107 • Faraday cup o Inexpensive o Simple mechanically & electrically o Less sensitive than electron multiplier Skoog, Fig. 11-2(b), 11-3 Ion Sources Basic Type Name and Acronym Ionizing Agent Gas phase Electron impact (EI) Energetic electrons Chemical ionization (CI) Reagent gaseous ions Field ionization (FI) High-potential electrode Desorption Field desorption (FD) High-potential electrode Electrospray ionization (ESI) High electrical field Matrix-assisted desorption/ionization (MALDI) Laser beam Plasma desorption (PD) Fission fragments from 252Cf Fast atom bombardment (FAB) Energetic atomic beam Secondary ion mass spectrometry (SIMS) Energetic beam of ions Thermospray ionization (TS) High temperature Skoog, Table 20-1 Electron Ionization (EI) • Electrons accelerated through potential of 70 V and interact with incoming molecules M + e– → M+• + e– + e– 70 eV Molecular ~55 eV 0.1 eV ion • Interaction with 70-eV Formaldehyde electron will likely remove electron with lowest ionization energy o n < < Harris, 6th ed., Fig. 22-3 Electron Ionization (EI) • Path of electrons & molecules are at right angles o Collide to produce mostly singly-charged positive ions • Inefficient process Skoog, Fig. 20-3 Chemical Ionization (CI) • Ionization source is filled with a reagent gas o CH4,C4H10, NH3,H2, CH3OH, NO • Energetic electrons (100 – 200 eV) convert CH4 to a variety of reactive products: CH 4 e CH 4 2 e CH 4 CH 4 CH 5 CH 3 CH 4 CH 3 H CH 3 CH 4 C 2 H 5 H 2 CH 5 M CH 4 MH C2H 5 M C2H 4 MH EI vs. CI Mass Spectra BASE PEAK • Hard source • Soft source o More fragmentation o Less fragmentation • Structural information • Molecular weight o Functional groups information Harris, Fig. 21-14 EI vs. CI Mass Spectra • 1-Decanol mass spectra • Hard source o More fragments o Structural info • Soft source o Less fragments o MW info Skoog, Fig. 20-2 Electrospray Ionization (ESI) • Sample typically in form of solution (organic or aqueous) • Excess solvent must be removed before entering MS o Large increase in pressure from solvent vaporization • Differential solvent removal o Solution passed through stainless steel capillary tube o Apply high electric potential (3 – 5 kV) o Solvent evaporates rapidly from droplet surface and droplets get smaller and smaller o Solvent molecules diffuse away Electrospray Ionization (ESI) Harris, 6th ed., Fig. 22-16 (b); (Skoog, Fig. 20-8) Laser Desorption Ionization (LDI) • Molecular system exposed to laser beam has its internal energy greatly increased o Melting o Vaporization o Ionization o Decomposition • Process of beaming laser light onto small area of sample specimen to desorb ions Herbert, C. G.; Johnstone, R. A. W.; Mass Spectrometry Basics; 2003, p. 8 Matrix-Assisted Laser Desorption Ionization (MALDI) • Aqueous/alcohol solution of sample is mixed with radiation-absorbing matrix to TOF-MS material o Matrices (Skoog, Table 20-4) • Solution evaporated on metallic probe surface • Solid mixture is exposed to pulsed laser beam o Analyte is sublimed as ions • Useful for obtaining accurate molecular weights of biopolymers Source: http://www.srsmaldi.com ESI & LDI Pioneers • Fenn (Virginia Commonwealth) & Tanaka (Shimadzu) • 2002 – Nobel Prize in Chemistry o "for the development of methods for John B. Fenn identification and structure analyses of biological macromolecules" o "for their development of soft desorption ionization methods for mass spectrometric analyses of Koichi Tanaka biological macromolecules" Source: http://www.nobel.se Fast Atom Bombardment (FAB) • Focus a high primary current beam of neutral atoms or molecules on sample • Sample dissolved in non-volatile liquid matrix • Inert gas atoms are ionized to give positive ions • As ions collide with other inert gas atoms (He, Ar, Xe), charge exchange occurs o Fast-moving ions become fast- moving atoms Source: http://www-methods.ch.cam.ac.uk/meth/ms/theory/fab.gif Secondary Ion Mass Spectrometry (SIMS) • Focus a high primary current beam of ions on sample • Sample dissolved in non- volatile liquid matrix • Dynamic SIMS o Current beam high enough to damage surface o Elemental and isotopic information obtained • Static SIMS o Dedicated to analysis of top monolayer of surface o Fresh layer of new ions continuously brought to surface Source: http://www.chemistry.wustl.edu/~walker/sims_exp.gif; http://www.ulb.ac.be/sciences/cpmct/images/logosims.gif Magnetic Sector (B) • Ions deflected according to their mass • Spectrum obtained by changing the field strength m B2r 2 z 2V m/z = mass-to-charge ratio B = magnetic field strength r = radii of curvature (trajectory) V = accelerating voltage Harris, 6th ed., Fig. 22-2; (Skoog, Fig. 20-12) Electrostatic Sector (E) • Ions deflected according to their kinetic energy o KE = ½mv2 Harris, 6th ed., Fig. 22-12 Double-Focusing • Combination of magnetic & electrostatic sectors o Improved resolving power • Resolution of 105 o Compatible with chromatographic columns o Compact • Configurations o Mattauch-Herzog • Skoog, Fig. 11-9 o Nier-Johnson • Skoog, Fig. 20-13 Mattauch-Herzog Source: http://www.oup.com/images/booksites/higson/higson_fig9.8.jpg Double-Focusing Ion Optics Forward Geometry EB Configuration (Nier-Johnson) Reverse Geometry BE Configuration Herbert, C. G.; Johnstone, R. A. W.; Mass Spectrometry Basics; 2003, p. 178-179 Time-of-Flight (TOF) Harris, 6th ed., Fig. 22-14; (Skoog, Fig. 11-8) Quadrupole (Q) Harris, Fig. 21-13; (Skoog, Fig. 11-4) Ion-Trap Harris, 6th ed., Fig. 22-15; (Skoog, Fig. 20-15) Hyphenated MS Methods • Mass spectrometer = detector for other analytical techniques o Mass spectra collected as compounds exit • Chromatography/MS o Gas Chromatography/MS (GC-MS) o Liquid Chromatography/MS (LC-MS) • Capillary Electrophoresis/MS (CE-MS) Chromatography/Mass Spectrometry • MS requires high vacuum o Avoid molecular collisions during ion separation • Chromatography is high-pressure technique o Must remove huge excess matter between the chromatograph and the spectrometer • For GC, narrow capillary column connected directly to inlet of the mass spectrometer • For LC, liquid from column creates huge volume of gas when vaporized o Pneumatically assisted electrospray o Atmospheric pressure chemical ionization (APCI) APCI • Uses heat and coaxial flow of N2 to convert eluate into a fine aerosol mist • Creates new ions from gas-phase reactions between ions & molecules • High voltage is applied to metal needle in the path of the aerosol Harris, 6th ed., Fig. 22-18 Liquid Chromatography/MS (LC-MS) Harris, 6th ed., Fig. 22-16 (a) Gas Chromatography/MS (GC-MS) • Must remove most of the carrier gas from the analyte • Quadrupole or ion trap mass analyzers used Skoog, Fig. 27-13, 27-14 Capillary Electrophoresis/MS (CE-MS) • Capillary effluent is passed into an electrospray ionization device • Products enter quadrupole mass analyzer • Detection limits: tens of femtomoles (10–14 M) Skoog, Fig. 30-7 Chromatography/MS Spectra GC CE Herbert, C. G.; Johnstone, R. A. W.; Mass Spectrometry Basics; 2003, p. 264 Tandem Mass Spectrometry (MS/MS) First MS Second MS • Isolates molecular ions • Fragments ions • Soft ionization source o Collisions between ions & He atoms cause o Molecular ions or protonated molecular ions further fragmentation • “Daughter” ions • “Parent” ions • Analogous to • Provides series of mass chromatographic column spectra for each molecular ion produced o Provides pure ionic species for second spectrometer QQQ Tandem Instrument • Q1 &Q3 are regular quadrupole filters • Q2 is a collision focusing chamber o Helium pumped into chamber & collides with parent ions o Operates in rf-mode only • Focuses scattered ions but does not act as a mass filter Skoog, Fig. 20-24 The Mass Spectrum • Molecular ion (M+•) = unknown molecular mass • M+• breaks apart efficiently with EI o Fragments provides clues about structure • CI mass spectrum has strong MH+ peak o Molecular mass information • Nitrogen Rule o Odd nominal mass for M+• • Odd # N atoms o Even nominal mass for M+• • Even # N atoms Harris, Fig. 21-14 Molecular Ion & Isotope Patterns • M+●peak is base peak for aromatic compounds o EI spectra • Next higher mass peak provides elemental composition info o M + 1 peak • Carbon Intensity of M + 1 relative to M+●for C H : o 98.92 % 12C n m Intensity = n × 1.08 % + m × 0.012 % o 1.08 % 13C • Hydrogen 13C 2H o 0.012 % 2H Benzene: Intensity = 6 × 1.08 % + 6 × 0.012 % = 6.55 % Biphenyl: Intensity = 12 × 1.08 % + 10 × 0.012 % = 13.1 % Harris, Fig. 21-18 Molecular Ion & Isotope Patterns Harris, Table 21-1 Rings and Double Bonds • Rings + double bonds (R + DB) formula o Used if composition of a molecular ion is known h n R DB c 1 2 2 c = # of Group 14 atoms (e.g., C, Si) [make 4 bonds] h = # of (H + halogen) atoms [make 1 bond] n = # of Group 15 atoms (e.g., N, P) [make 3 bonds] 22 11 11 R DB 14 1 15 rings & double bonds 2 2 Harris, 6th ed., p.
Load more

Recommended publications
  • Chemistry: the Molecular Nature of Matter and Change
    REVISED CONFIRMING PAGES The Components of Matter 2.1 Elements, Compounds, and 2.5 The Atomic Theory Today 2.8 Formula, Name, and Mass of Mixtures: An Atomic Overview Structure of the Atom a Compound 2.2 The Observations That Led to Atomic Number, Mass Number, and Binary Ionic Compounds an Atomic View of Matter Atomic Symbol Compounds That Contain Polyatomic Mass Conservation Isotopes Ions Definite Composition Atomic Masses of the Elements Acid Names from Anion Names Multiple Proportions 2.6 Elements: A First Look at the Binary Covalent Compounds The Simplest Organic Compounds: Dalton’s Atomic Theory Periodic Table 2.3 Straight-Chain Alkanes Postulates of the Atomic Theory Organization of the Periodic Table Masses from a Chemical Formula How the Atomic Theory Explains Classifying the Elements Representing Molecules with a the Mass Laws Compounds: An Introduction 2.7 Formula and a Model to Bonding 2.4 The Observations That Led to Mixtures: Classification and the Nuclear Atom Model The Formation of Ionic Compounds 2.9 Separation Discovery of the Electron and The Formation of Covalent An Overview of the Components of Its Properties Compounds Matter Discovery of the Atomic Nucleus (a) (b) (right) ©Rudy Umans/Shutterstock IN THIS CHAPTER . We examine the properties and composition of matter on the macroscopic and atomic scales. By the end of this chapter, you should be able to • Relate the three types of matter—elements or elementary substances, compounds, and mixtures—to the simple chemical entities that they comprise—atoms, ions, and molecules;
    [Show full text]
  • 20.5 Ion Detectors
    20.5 Ion Detectors • the Faraday cup neutralizes ions to provide a high-precision measurement • the electron multiplier generates a pulse of current for each ion • the photon multiplier uses conversion dynodes to monitor both positive and negative ions • the two multipliers are capable of fast measurements, thus compatible with TOF or Fourier transform methods 20.5 : 1/4 Faraday Cup slit Ions exiting the analyzer are slowed by Faraday cup a positive potential and impact the ion + grounded electrode. At the electrode beam + they are __________ by electrons that RL travel through the load resistor. This ion suppressor causes a voltage across the load resistor that is measured by a high input impedance voltmeter. The impacted electrode is at an angle so that any secondary ions that are created are _____________ by the grounded wall. Of all ion detectors, the Faraday cup provides the most precise relationship between the number of ions exiting the analyzer and the electrical measurement. It is used in __________ experiments such as isotope dilution. Because very small currents are measured, the Faraday cup cannot be used for experiments involving rapid scanning. 20.5 : 2/4 Electron Multiplier ion beam An electron multiplier is constructed just like a photomultiplier but without 16e- 4e- 3 - a _______________. It has dynodes 10 e RL constructed from a Cu/Be alloy, which dynodes is a good secondary electron emitter. +V The dynode potentials are such that the first is grounded and each subsequent one is 100 V more positive. This makes the voltage measurement a little tricky because one end of the load resistor is connected to positive _____________.
    [Show full text]
  • Integrated M.Sc. Chemistry (CBCS) SYLLABUS Department of Chemistry Central University of Tamil Nadu Thiruvarur 610
    Integrated M.Sc. Chemistry (CBCS) SYLLABUS Department of Chemistry Central University of Tamil Nadu Thiruvarur 610 101 Name of the course : Integrated M. Sc. (Chemistry) Duration : 10 semesters Intake : 30 Eligibility : Plus two examination or equivalent of any recognized board in India with 60% marks (Chemistry, Mathematics, Physics and Computer Science/Biology) for general category, 55% marks for OBC (Non-creamy layer) and 50% marks for SC/ST candidates. The candidates should not have completed 20 years of age as on 01-07-2015. Course Structure The five year program is spread into ten semesters where in first four semesters are designed for broad subject based understanding. Later six semesters will have increased focus on chemistry. The subject courses in the early stage of iM.Sc programme are simplified and of basic level that bolsters the inter-disciplinary way of learning. The third and subsequent year courses have been designed on advanced theories in chemistry with emphasis on concurrent modern laboratory techniques. Further the iM.Sc (Chemistry) programme has been included with experiments that provide exhaustive hands on experience on various sophisticated instruments, experimental techniques to enable the students secure jobs in corporate. The final semester is dedicated to specialization within the subject with research level training. The rules and regulations of Choice Based Credit System (CBCS) are applicable to this program. Generally, a student takes ten semesters to complete the program. The courses offered under CBCS, has certain credit number (2, 3 or 4). Core requirements of the programs are clearly defined. In the first two years of the program, a student has common course load with students from other departments.
    [Show full text]
  • Modern Mass Spectrometry
    Modern Mass Spectrometry MacMillan Group Meeting 2005 Sandra Lee Key References: E. Uggerud, S. Petrie, D. K. Bohme, F. Turecek, D. Schröder, H. Schwarz, D. Plattner, T. Wyttenbach, M. T. Bowers, P. B. Armentrout, S. A. Truger, T. Junker, G. Suizdak, Mark Brönstrup. Topics in Current Chemistry: Modern Mass Spectroscopy, pp. 1-302, 225. Springer-Verlag, Berlin, 2003. Current Topics in Organic Chemistry 2003, 15, 1503-1624 1 The Basics of Mass Spectroscopy ! Purpose Mass spectrometers use the difference in mass-to-charge ratio (m/z) of ionized atoms or molecules to separate them. Therefore, mass spectroscopy allows quantitation of atoms or molecules and provides structural information by the identification of distinctive fragmentation patterns. The general operation of a mass spectrometer is: "1. " create gas-phase ions "2. " separate the ions in space or time based on their mass-to-charge ratio "3. " measure the quantity of ions of each mass-to-charge ratio Ionization sources ! Instrumentation Chemical Ionisation (CI) Atmospheric Pressure CI!(APCI) Electron Impact!(EI) Electrospray Ionization!(ESI) SORTING DETECTION IONIZATION OF IONS OF IONS Fast Atom Bombardment (FAB) Field Desorption/Field Ionisation (FD/FI) Matrix Assisted Laser Desorption gaseous mass ion Ionisation!(MALDI) ion source analyzer transducer Thermospray Ionisation (TI) Analyzers quadrupoles vacuum signal Time-of-Flight (TOF) pump processor magnetic sectors 10-5– 10-8 torr Fourier transform and quadrupole ion traps inlet Detectors mass electron multiplier spectrum Faraday cup Ionization Sources: Classical Methods ! Electron Impact Ionization A beam of electrons passes through a gas-phase sample and collides with neutral analyte molcules (M) to produce a positively charged ion or a fragment ion.
    [Show full text]
  • Project Note Weston Solutions, Inc
    PROJECT NOTE WESTON SOLUTIONS, INC. To: Canadian Radium & Uranium Corp. Site File Date: June 5, 2014 W.O. No.: 20405.012.013.2222.00 From: Denise Breen, Weston Solutions, Inc. Subject: Determination of Significant Lead Concentrations in Sediment Samples References 1. New York State Department of Environmental Conservation. Technical Guidance for Screening Contaminated Sediments. March 1998. [45 pages] 2. U.S. Environmental Protection Agency (EPA) Office of Emergency Response. Establishing an Observed Release – Quick Reference Fact Sheet. Federal Register, Volume 55, No. 241. September 1995. [7 pages] 3. International Union of Pure and Applied Chemistry, Inorganic Chemistry Division Commission on Atomic Weights and Isotopic Abundances. Atomic Weights of Elements: Review 2000. 2003. [120 pages] WESTON personnel collected six sediment samples (including one environmental duplicate sample) from five locations along the surface water pathway of the Canadian Radium & Uranium Corp. (CRU) site in May 2014. The sediment samples were analyzed for Target Analyte List (TAL) Metals and Stable Lead Isotopes. 1. TAL Lead Interpretation: In order to quantify the significance for Lead, Thallium and Mercury the following was performed: 1. WESTON personnel tabulated all available TAL Metal data from the May 2014 Sediment Sampling event. 2. For each analyte of concern (Lead, Thallium, and Mercury), the highest background concentration was selected and then multiplied by three. This is the criteria to find the significance of site attributable release as per Hazard Ranking System guidelines. 3. One analytical lead result (2222-SD04) of 520 mg/kg (J) was qualified with an unknown bias. In accordance with US EPA document “Using Data to Document an Observed Release and Observed Contamination”, 2222-SD03 lead concentration was adjusted by dividing by the factor value for lead of 1.44 to equal 361 mg/kg.
    [Show full text]
  • ISOTOPIC ELEMENTS) and the WHOLE NUMBER RULE for ATOMIC WEIGHTS by William D
    624 CHEMISTRY: W. D. HARKINS PROC. N. A. -S. -To summarize, the mechanism tentatively proposed above may be dia.. grammatically represented as follows: Insulin Glycogen-*Hexose ---Hexose mono-phosphate Hexose di-phosphate-<r-Triose phosphate and Reactive triose Carbon Lactic dioxide acid and Water 1 It has recently been noted from the Zentralblatt that Euler and Myrback (Svensk. Kem. Tidskr., 36, 295-306 (1924)) have made an apparently similar suggestion. As the originAl article has not been available it has been impossible to learn how closely the two theories coincide. 2R. Robison, Biochem. J., 16, 809 (1922). 'This step has been definitely established by Harden and his co-workers and the enzyme accomplishing the change has been named hexosephosphatase. 4 Neuberg and Kerb, Biocerm. Zs., 58, 158-170. (1913). ' Euler and Myrback, Chemie Zele Gewebe, 12, 57 (1925). THE SEPARATION OF CHLORINE INTO ISOTOPES (ISOTOPIC ELEMENTS) AND THE WHOLE NUMBER RULE FOR ATOMIC WEIGHTS By WILLiAM D. HARKINs KENT CHEMICAL LABORATORY, UNIvRSITY OP CHCAGO Comminicated August 26, 1925 Introduction.-The existence of isotopes among the heaviest or radio- active elements was demonstrated by the difference in the rays emitted by "different radioactive elements of almost identical chemical properties" now designated as isotopes of the same chemical element. Isotopes have been shown to exist in the light elements by two independent methods: by their detection in the positive ray method, and by the actual separation of the isotopes. The earliest use of the positive ray method for detecting isotopes by J. J. Thomson' resulted in the discovery of the isotopes of neon, while the separation of chlorine into isotopic fractions by Harkins and Downloaded by guest on September 25, 2021 VOL.
    [Show full text]
  • Analytical Chemistry, Strategic Exercise: Organic Aerosol Analysis
    WIR SCHAFFEN WISSEN –HEUTE FÜR MORGEN Analytical Chemistry, Strategic exercise: Organic aerosol analysis Urs Baltensperger Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen , Switzerland ETHZ, HS 2020, 8.12.2020 Aerosol size distribution, and sources and sinks Chemical composition of PM1 in Zurich in winter Energiespiegel 19/2008 http://gabe.web.psi.ch/pdfs/Energiespiegel_19_e.pdf Today’s task: Organic aerosol analysis Page 4 The state of the art in 2009 Hallquist et al., ACP 2009 Traditional methods can identify only a fraction of organics Rogge et al., 1993 Most detailed analysis performed with off-line methods: More than 10‘000 different organic compounds isolated with GCxGC-TOF/MS Hamilton et al., 2004 NB: isolated ≠ identified…. Besides extraction, also thermal desorption is applied: TAG (Goldstein et al., 2008) Organic acids formed in the photooxidation of -pinene All acids found in aerosol phase. Some of them are highly volatile (e.g., formic, acetic acid) and not expected to be there. Probably hydrolysis of oligomers Fisseha et al., Anal. Chem. 2004 Developments since 2009 EESI CHARON‐ PTRMS FIGAERO -I-CIMS Adapted from Hallquist et al., 2009 9 Required for mass spectrometry: ionization of individual molecules • For gas phase: relatively easy (avoid fragmentation, clustering) • For aerosol particles: Much more difficult: either dissolution in a solvent or evaporation - Problem with dissolution: only the soluble fraction accessible - Problem with evaporation: fragmentation Page 10 What is Mass Spectrometry
    [Show full text]
  • QMG 422 Analyzers
    Operating Instructions Incl. Declaration of Conformity QMG 422 Analyzers BG 805 983 BE (0112) 1 Product Identification In all communications with Pfeiffer Vacuum, please specify the information on the product nameplate. For convenient reference copy that information into the space provided below. Pfeiffer Vacuum, D-35614 Asslar Typ: No: F-No: Validity This document applies to the QMA 400, QMA 410, QMA 430 with Faraday cup or 90° off-axis SEM and Faraday cup and with the ion sources described in this document. Illustrations If not indicated otherwise in the legends, the illustrations in this document corre- spond to the QMA 400 with 90° off-axis SEM. They apply to other types by analogy. Designations The short designation "QMA" is used for the QMA 400, QMA 410 and QMA 430. The short designation "QMH" is used for the QMH 400 and QMH 410. In contrast to the operating instructions for the QMG 422, these instructions follow the same conventions as the Pfeiffer QuadStar™ 422 operating instructions. The parameters are marked with quotation marks ("…") e.g. "Resolution". Technical changes We reserve the right to make technical changes without prior notice. Intended Use The QMA 400, QMA 410 and QMA 430 Analyzers are used for gas analysis in high vacuum. They are part of the QMG 422 mass spectrometer system and may only be used in connection with equipment belonging to that system. The operating instructions of all system components must be strictly followed. 2 BG 805 983 BE (0112) QMA4x0.oi Contents Product Identification 2 Validity 2 Intended
    [Show full text]
  • Electron Microscopy Are the Beam Damaging Effects That Can Arise from Interactions Between the Primary High Energy Electron Beam and the Sample
    Thermal in situ TEM experiment on nanoscale indium islands Estimation of Electron Beam Heating Effect Master’s thesis in Applied Physics REN QIU Department of Physics CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden 2017 Master’s thesis 2017 Thermal in situ TEM experiment on nanoscale indium islands Estimation of Electron Beam Heating Effect REN QIU Department of Physics Eva Olsson Group Chalmers University of Technology Gothenburg, Sweden 2017 Thermal in situ TEM Experiment on Nanoscale Indium Islands Estimation of Electron Beam Heating Effect Master Thesis within the Masters Programme of Applied Physics © REN QIU, 2017. Supervisor: Eva Olsson, Norvik Voskanian, Lunjie Zeng, Department of Physics Examiner: Eva Olsson, Department of Physics Master’s Thesis 2017 Department of Physics Eva Olsson Group Chalmers University of Technology SE-412 96 Gothenburg Telephone + 46(0)73-732 4883 Cover: Top left: Indium islands segmentation by watershed algorithm based on the bright field TEM image. Top right: Dark field image of the in situ melting experiment where the indium islands with bright pixels are melted and the ones with dark pixels are in solid state. Bottom left: Nano-scale gold tip fabricated through electrochemical etching. Bottom right: A simple Faraday cup made on the gold tip by focus ion beam (FIB) method. Printed by Chalmers Reproservice Gothenburg, Sweden 2017 iv Thermal in situ TEM Experiment on Nanoscale Indium Islands Estimation of Electron Beam Heating Effect REN QIU Department of Physics Chalmers University of Technology Abstract One of the limitations of transmission electron microscopy are the beam damaging effects that can arise from interactions between the primary high energy electron beam and the sample.
    [Show full text]
  • Mass Spectrometer Hardware for Analyzing Stable Isotope Ratios
    Handbook of Stable Isotope Analytical Techniques, Volume-I P.A. de Groot (Editor) © 2004 Elsevier B.V. All rights reserved. CHAPTER 38 Mass Spectrometer Hardware for Analyzing Stable Isotope Ratios Willi A. Brand Max-Planck-Institute for Biogeochemistry, PO Box 100164, 07701 Jena, Germany e-mail: [email protected] Abstract Mass spectrometers and sample preparation techniques for stable isotope ratio measurements, originally developed and used by a small group of scientists, are now used in a wide range of fields. Instruments today are typically acquired from a manu- facturer rather than being custom built in the laboratory, as was once the case. In order to consistently generate measurements of high precision and reliability, an extensive knowledge of instrumental effects and their underlying causes is required. This con- tribution attempts to fill in the gaps that often characterize the instrumental knowl- edge of relative newcomers to the field. 38.1 Introduction Since the invention of mass spectrometry in 1910 by J.J. Thomson in the Cavendish laboratories in Cambridge(‘parabola spectrograph’; Thompson, 1910), this technique has provided a wealth of information about the microscopic world of atoms, mole- cules and ions. One of the first discoveries was the existence of stable isotopes, which were first seen in 1912 in neon (masses 20 and 22, with respective abundances of 91% and 9%; Thomson, 1913). Following this early work, F.W. Aston in the same laboratory set up a new instrument for which he coined the term ‘mass spectrograph’ which he used for checking almost all of the elements for the existence of isotopes.
    [Show full text]
  • Probe Current Determination in Analytical TEM/STEM and Its Application to the Characterization of Large Area EDS Detectors
    University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 2015 Probe current determination in analytical TEM/ STEM and its application to the characterization of large area EDS detectors David R. G Mitchell University of Wollongong, [email protected] MItchell John Bromley Nancarrow University of Wollongong, [email protected] Publication Details Mitchell, D. R. G. & Nancarrow, M. J. B. (2015). Probe current determination in analytical TEM/STEM and its application to the characterization of large area EDS detectors. Microscopy Research and Technique, 78 (10), 886-893. Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Probe current determination in analytical TEM/STEM and its application to the characterization of large area EDS detectors Abstract A simple procedure, which enables accurate measurement of transmission electron microscopy (TEM)/STEM probe currents using an energy loss spectrometer drift tube is described. The currents obtained are compared with those measured on the fluorescent screen to enable the losses due to secondary and backscattered electrons to be determined. The current values obtained from the drift tube allow the correction of fluorescent screen current densities to yield true current. They also enable CCD conversion efficiencies to be obtained, which in turn allows images to be calibrated in terms of electron fluence. Using probes of known current in conjunction with a NiO reference specimen enables the X-ray detector solid angle to be determined. The iON specimen also allows a wide range of other EDS detector parameters to be obtained, including the presence of ice and carbon contamination.
    [Show full text]
  • Neutron 'Octaves'
    Neutron `Octaves’ in the Moon Nuclear Model: A Harmonic Ordering of the Stable Isotopes1 Laurence Hecht May 18, 2007 Summary: When the stable isotopes are grouped according to the four Platonic solid shells, as described by the Moon model of the nucleus, the number of neutrons is found to fall in “octaves.” Thus, for the first 135 stable isotopes: 1H to 15N, number of neutrons = 0 to 8 16O to 30Si , number of neutrons = 8 to 16 31P to 58Fe, number of neutrons = 16 to 32 59Co to 110Pd, number of neutrons = 32 to 64. The Moon structure of the nucleus thus defines a periodicity in the gross ordering of the stable isotopes, somewhat analogous to the periods of the Mendeleyev table of the elements, but based on an implicit musical harmony. Introduction The ordering of the elements by atomic weight shows a periodicity discovered by Dmitri Mendeleyev in 1869. Mendeleyev found that increase in mass was not a linear property as suggested by Galileo and Newton, but rather evidenced a periodicity. When arranged in rows by order of increasing mass, properties including the propensity to chemical combination, valence, reactivity, melting and boiling points, crystal structure and others show a periodically repeating character, such that elements falling in the same 1 Author’s Note: Although the discovery reported here was subsumed within the previously published item, “A New Approach to the Ordering Principle of the Stable Isotopes” (21st Century Science & Technology, Fall 2007), it received insufficient elaboration there for the great majority of readers to grasp. This more complete and contemporaneous account of the discovery of the neutron “octaves” is provided to remedy that shortcoming (December 2, 2008).
    [Show full text]