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Questions and Answers
What is indicated by the formula $a \sin(\theta) = m \lambda$ in diffraction?
What is indicated by the formula $a \sin(\theta) = m \lambda$ in diffraction?
X-ray diffraction occurs due to the scattering of X-rays from atomic planes in a crystal.
X-ray diffraction occurs due to the scattering of X-rays from atomic planes in a crystal.
True
Name the seven crystal classes based on unit cell parameters.
Name the seven crystal classes based on unit cell parameters.
Triclinic, Monoclinic, Orthorhombic, Tetragonal, Cubic, Trigonal, Hexagonal
The quality of occurring at regular intervals in time or space is known as __________.
The quality of occurring at regular intervals in time or space is known as __________.
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What does the ionization cross-section indicate?
What does the ionization cross-section indicate?
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Match the crystal classes with their characteristics:
Match the crystal classes with their characteristics:
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The wider arrows indicate the least intense lines in the energy diagram.
The wider arrows indicate the least intense lines in the energy diagram.
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How many Bravais Lattices are defined in three-dimensional crystals?
How many Bravais Lattices are defined in three-dimensional crystals?
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What are the names of the series indicated for the X-ray levels?
What are the names of the series indicated for the X-ray levels?
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Miller indices is a system used to designate crystal planes.
Miller indices is a system used to designate crystal planes.
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The _______ factors are essential in determining the intensity of scattered X-rays.
The _______ factors are essential in determining the intensity of scattered X-rays.
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What is the primary purpose of unit cells in crystallography?
What is the primary purpose of unit cells in crystallography?
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Match the following types of indices with their definitions:
Match the following types of indices with their definitions:
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Which of the following statements is true regarding phase interference?
Which of the following statements is true regarding phase interference?
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Intensity calculations in X-ray scattering are based solely on the energy levels of electrons.
Intensity calculations in X-ray scattering are based solely on the energy levels of electrons.
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What role does the ionization cross-section play in X-ray emission?
What role does the ionization cross-section play in X-ray emission?
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What is the primary advantage of using Copper (Cu) as an anode material?
What is the primary advantage of using Copper (Cu) as an anode material?
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The wavelength of emitted X-rays changes with increasing atomic number according to Moseley’s law.
The wavelength of emitted X-rays changes with increasing atomic number according to Moseley’s law.
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What is the relationship between intensity and applied voltage in X-ray tubes?
What is the relationship between intensity and applied voltage in X-ray tubes?
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The formula for the intensity of K-line is I K-line = B_i (V - V_k)^{______}
The formula for the intensity of K-line is I K-line = B_i (V - V_k)^{______}
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Match the following anode materials with their characteristics:
Match the following anode materials with their characteristics:
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Which K-line is always stronger than Kα2?
Which K-line is always stronger than Kα2?
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Soft X-rays are emitted from the K shells of atoms.
Soft X-rays are emitted from the K shells of atoms.
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What does the work function W_K represent in the context of X-ray emission?
What does the work function W_K represent in the context of X-ray emission?
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According to Moseley’s law, the formula for the wavelength of the emitted X-ray is 1/λ = K(Z - ______)^2.
According to Moseley’s law, the formula for the wavelength of the emitted X-ray is 1/λ = K(Z - ______)^2.
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What characteristic is associated with the intensity calculation for emitted X-rays?
What characteristic is associated with the intensity calculation for emitted X-rays?
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Study Notes
Course Information
- Course: IN-201: Analytical Instrumentation
- Academic Year: Aug-Dec 2024
- Instructor: Dr. Manukumara Manjappa ([email protected])
- Office: #113 IAP
- Teaching Assistants: Mr. Om Prakash Sahu ([email protected]) and Ms. Santilata Sahoo ([email protected])
- Class Timings: 5:00 PM - 6:30 PM on Mondays and Wednesdays
- Credits: 3
- Venue: Instrumentation and Applied Physics (IAP) Department, Lecture hall (LH)-1
- Guest Lectures: Prof. Asokan. S and Prof. Soumen Ghosh
Course Content
- X-Ray Methods of Analysis - Test I
- Electron Methods of Analysis - Test II
- STM, TEM, AFM Techniques - Test II
- UV, Vis, IR and THz spectroscopy
- Mass spectroscopy and Thermal Analysis Techniques - Test III
- Raman Spectroscopy - Test III
- Polarimetry Techniques
- Nuclear Magnetic resonance - Final Exam
- Mid Terms (Best of Two) 40% + Final Exam (60%)
Learning Objectives
- Fundamental Principles of Analytical Instrumentation
- Instrumentation Techniques
- Operation and working Procedures
- Instrument Selection
- Measurement and Calibrations
- Data Analysis
- Applications
References
- Principles of Instrumental Analysis - Skoog et al
- X-ray Methods - Clive Whiston
- Instrumental Techniques for Analytical Chemistry – Frank Settile
- EDXA in Electron Microscope – A.J. Garrath-Reed & Bell
- Electron Diffraction in TEM – P.E. Champress
- Elements of X-ray Diffraction – BD Cullity & S R Stock
- Fundamentals of Molecular Spectroscopy – CN Banwell
- Instrumental methods of analysis, by Willard, H H; Merritt, Jr, L L; Dean, J A.
- Analytical Instrumentation: A Guide to Laboratory, Portable and Miniaturized Instruments, by Gillian McMahon
Analytical Instruments
- Microscope
- Atomic Force Microscope
- Scanning electron microscope (SEM)
- UV-Vis Spectrometer
- NMR (Nuclear Magnetic Resonance)
Analytical Instrumentation: Introduction and Definition
- An instrument is a device that enables analytical measurements to be carried out automatically and objectively.
- Analytical instruments help analysts to work out composition, characterize samples, separate mixtures and yield useful results and analysis in both qualitative and quantitative ways.
- Components of an analytical instrument include stimulus, input transducer (detector), signal processor (amplifier, digitizer), and readout (meter, plotter, or computer).
Analytical Process: Flow Chart
- Steps for an analytical process include defining problems, gathering information, deciding instrument and methods, making a plan, obtaining samples, carrying out work, considering validity, interpreting data, and communicating results.
Instruments for Analysis
- Stimulus: energy source (electromagnetic radiation, electrical signals, mechanical force, and thermal energy)
- System under study: materials, solutions, biological samples, and devices
- Analytical information: nonelectrical domain (physical and chemical domain), electrical domain (analog, time, frequency domain signals, digital signals),
Analytical Information
- Analog-domain signals: continuous-time, continuous-value signals
- Time-domain information: describes the relationships of signal fluctuations over time
- Digital information: data encoded in a two-level scheme for measurements.
Transducers, Sensors, and Detectors
- Transducer: Converts nonelectrical information to electrical information, and vice-versa
- Sensor: Analytical device that monitors specific chemical species continuously and reversibly (continuously and reversibly).
- Detector: Device that identifies, records, or indicates a change in one of the variables (pressure, temperature, etc.) in the environment.
Classical Methods
- Gravimetric: Measurement of mass for quantitative analysis of analyte (using weighing balances). These methods are analytical, simple, lab-based, affordable, and time-tested
- Volumetric: Measurement of volume to facilitate quantitative analysis by titrations (volume in liquid measurements). This is an analytical chemistry technique.
Instrumental Methods (further subdivided into optical and electro-analytical)
- Optical methods involve interactions of analyte with EM radiation, Spectroscopy, techniques, Emission and scattering measurements.
- Electro-analytical methods involve measurement of physical/chemical properties.
Qualitative Analysis
- Qualitative analysis determines the identity or composition of a substance (what is present). Example: identifying elements or compounds in a sample through physical or chemical experiments; a fingerprint spectrum is characteristic.
Quantitative Analysis
- Quantitative analysis determines the amount or concentration of a substance (in a sample) (how much is present). This helps in obtaining the quantities of an analyte using techniques like Beer's Law
Selecting an Analytical Method
- Selection factors include: defining the analytical problem, required accuracy, knowledge of sample concentration/density range, needed physical/chemical property of a sample, instrument performance. Factors in instrument performance are: precision, sensitivity, detection limit, dynamic range, and selectivity.
Performance Characteristics of the Instrumental Analysis
- Precision (measuring agreement of data sets), by calculating standard deviation.
- Sensitivity (ability to distinguish small changes in concentration) which is represented by the slope of a calibration curve.
- Detection Limit (minimum measurable concentration), is the signal strength of a blank (no analyte) sample (noise).
- Dynamic Range : This determines the range from the smallest concentration to the largest (linearity is required) and limits the practical range
- Selectivity (freedom from interference from other substances): The ratio between the concentrations of the interferer and analyte must be small otherwise the results of the experiment are inaccurate.
X-Ray Methods of Analysis
- Basics of X-rays, instrumentation (source, monochromator/filter, detector), basics of X-ray analysis (interaction of X-rays with matter, Absorption, scattering and diffraction)
- Applications: X-ray diffraction, X-ray Fluorescence, X-ray photoelectron spectroscopy.
- Accidental Discovery by Rontgen: Description
- Aftermath of X-rays discovery: Birth of Radiology, discovery of electrons, discovery of radioactivity, determining crystal structures (X-ray diffraction), and imaging DNA structure.
- X-rays as EM radiation: wavelength, ionizing radiation, and radioactivity, and radiographic applications
- Relevant formulas: E=hc/λ , v=c/λ , v=1/λ, T = 1/v. Definitions: E = energy (eV) , X = wavelength (m), v = wavenumber (m-1), T = period (s), v = frequency (s-1 or Hz), h = Planck’s constant, c = speed of light.
Production of X-rays:
- X-ray production in vacuum tubes: Fast-moving charged particles (electrons), striking metal target cause X-rays
- Kinetic energy: eV=1/2mv2
- Continuous (Bremsstrahlung) X-rays : due to deceleration of electrons, this results in a wide range of X-ray energies
- Characteristic X-rays: Specific X-ray lines emitted when electrons jump to inner shells
- X-ray tube components: cathode filament, vacuum chamber, target, high voltage, accelerating electrons.
X-Ray Detectors
- Photographic Films: Record intensity of X-ray
- Gas Filled: Produce ion pairs. The number of ion pairs corresponds to the intensity.
- Scintillation: Light flashes proportional to X-ray energy, detected by PMT.
- Semiconductor: Directly measure the energy of X-rays, and the number of electron-hole pairs is proportional to the X-ray energy.
Film Photography: Detection Process
- Silver halide grains, gelatin matrix, chemical reduction process (upon X-ray exposure)
- Invisible image (latent image), Formation of a grain.
- Development of film (developer chemicals) producing a dark area (exposed grains).
Film Selection
- Factors in selecting films for radiography : Composition, shape, size of the part being examined, type of radiation (X-rays, gamma rays), available kilovoltages or gamma radiation intensity
- Importance of high radiographic detail or swift and affordable analysis for the procedure
Gas Filled/ Proportional Detectors (Counters)
- Number of Ion Pairs: Transfer of energy, equal to the ionization energy (or work function).
- Dependence on: type of gas / species gas; type of radiation, energy of incident radiation.
- Gas filled detectors: Types of gas-filled detectors
- Different detection regimes: Recombination region, Ionization region, Proportional region, and Geiger region (also called Geiger-Müller region).
- Various features: ionization chamber, proportional counters, Geiger counters
- W-Value: Defined as the average energy loss by incident particle per ion pair
Scintillation Detectors: Schematic
- Thallium-activated Nal, Sodium activated CsI, Bismuth germanate (BGO)
- Increasing voltages in subsequent dynodes (PMT) for multiplication signal strength
- Energy resolution in scintillation detection: 2-3 times better compared in proportional detectors
Inorganic Scintillators: Band Structure and light emission process
- Emission spectra (200-600 nm)
- Excitation/Band gap
- Activation centers (impurities)
- Light emission processes
- Organic scintillators
- Scintillation materials (organic and inorganic).
- Characteristics (e.g., high Z, fast decay times, and cost).
- Inorganic scintillator types (e.g. alkali halide, slow/fast inorganics.)
X-Ray Fluorescence Spectroscopy
- Absorption of X-rays results in excitation. This is followed by emission of characteristic x-rays
- Absorption of X-rays causes ionization from inner shells; electrons filling the vacancy emit characteristic X-rays.
- The emitted fluorescence X-rays are characteristic to the element.
- Conditions for X-ray fluorescence emission
- Fluorescence yield:
- dependence on atomic number
- low Z elements, high Z elements
X-Ray Fluorescence Methods
- Wavelength dispersive XRF (WDXRF), energy dispersive XRF (EDXRF)
- Components of WDXRF techniques
- Components of EDXRF techniques; Detectors such as p-type Si(Li) detector, Amplifier, Multichannel analyzer
X-Ray Fluorescence Analysis
- Qualitative analysis: Determining the presence of elements
- Quantitative analysis: Estimating the concentration of elements in a sample
- Factors affecting XRF intensity
- Matrix absorption
- Multiple excitation
- Applications of XRF
- Film thickness determination
Summary of X-Ray Interactions with Matter
- Types of interactions; Coherent scattering, Photoelectric effect, Compton effect, Pair Production, Photo Disintegration
- Energy dependence
- Penetration depth
Summary of X-Ray Diffraction Methods
- Laue Diffraction, Rotating Crystal Method.
- Powder Diffraction, Transmission Method (Debye-Scherrer Method/ and Pinhole method);
- Focusing Method (Diffractometer)
Crystal Structure Determination
- Crystal structure features: symmetry, periodicity
- Lattice parameters
- Miller indices
- Bragg's law
- Indexing diffraction patterns
- Selection rules for various Bravais lattices
Applications of Powder Diffraction Method
- Qualitative analysis (phase identification)
- Crystallite size and strain determination
X-Ray Diffractometer:
- Components: X-ray tube, diffraction circle, divergence slits, receiving slits, specimen target, counter
Analysis of X-ray diffraction patterns:
- Determining d-spacing, indexing diffracted beams and calculating parameters needed for crystal characterization (unit-cell dimensions, atomic positions and symmetry)
Software used for analysis of Powder Data
- Difpatan; ZDS; AXES.zip; BREADTH.zip; FARHAN
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Description
Test your knowledge on X-ray diffraction, crystal classes, and the principles of crystallography. This quiz covers essential concepts such as Miller indices, ionization cross-section, and Bravais lattices. Challenge yourself with questions related to the characteristics of crystal structures and their implications in X-ray scattering.
