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SpectroscopIC aNALYSIS Part 7 – X-ray Analysis Methods. Chulalongkorn University, Bangkok, Thailand January 2012 Dr Ron Beckett Water Studies Centre & School of Chemistry Monash University, Melbourne, Australia Email: [email protected] Water Studies Centre. 1.

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Spectroscopic analysis part 7 x ray analysis methods

SpectroscopIC aNALYSISPart 7 – X-ray Analysis Methods

Chulalongkorn University, Bangkok, Thailand January 2012

Dr Ron Beckett

Water Studies Centre & School of ChemistryMonash University, Melbourne, Australia

Email: [email protected]

Water

Studies

Centre

1


X ray analysis methods

X-ray Analysis Methods

  • Properties of X-radiation

  • X-ray diffraction

  • X-ray emission spectroscopy

  • Production of X-radiation in an X-ray tube

  • X-ray fluorscence

2


Properties of x radiation

Properties of X-radiation

  • Frequency n3x1016 – 3x1018Hz

  • Wavelength l10 nm – 100 pm

  • High energy radiation, damaging to biological cells

  • High penetration of materials due to low absorbance is useful in medicine (body X-rays) and material science (fracture detection)

3


Spectroscopic analysis part 7 x ray analysis methods

4


X ray imaging in medicine and dentistry

X-ray Imaging in Medicine and Dentistry

5


X ray diffraction by crystals

X-ray Diffraction by Crystals

X-rays are reflected from planes of atoms in the crystal lattice of compounds

6


X ray diffraction by crystals1

X-ray Diffraction by Crystals

X-rays reflected from two planes of atoms in the crystal lattice constructively interfere only when the path length difference is an integral number of wavelengths

7

For waves 1 and 2 path lengths BC + CD = l , 2 l , 3l , ...., n l


X ray diffraction by crystals2

X-ray Diffraction by Crystals

This condition results in the following law for X-ray diffraction by crystals

8


X ray powder diffraction patterns

X-ray Powder Diffraction Patterns

Direction of incident beam

Diffracted beams

9

Random orientation of crystals in the powder


X ray powder diffraction camera

X-ray Powder Diffraction Camera

10


X ray powder diffraction camera1

X-ray Powder Diffraction Camera

11


X ray powder diffractometer

X-ray Powder Diffractometer

12


X ray powder diffractometer1

X-ray Powder Diffractometer

13


Spectroscopic analysis part 7 x ray analysis methods

X-ray Powder Diffraction Patternsare used to identify crystalline materials and to determine the amount of each phase in a mixture

14


Single crystal x ray crystallography

Single Crystal X-ray Crystallography

Analysis of the geometry and intensity of spots enables the crystal and molecular structure of compounds to be determined

15


X ray studies lead to the discovery of the double helix structure of dna

X-ray Studies Lead to the Discovery of the Double Helix Structure of DNA

16

Rosalyn Franklin Single crystal X-ray pattern of DNA


Single crystal x ray diffraction monochrometers

Single Crystal X-ray Diffraction Monochrometers

17


Single crystal x ray diffraction monochrometers1

Single Crystal X-ray Diffraction Monochrometers

18


X ray emission spectrometer

X-ray Emission Spectrometer

Monochrometer

Excitation Source

electrons

protons

X-rays

g-rays

19


X ray emission

X-ray Emission

Excitation Source

electrons

protons

X-rays

g-rays

X-ray Emission


X ray emission1

X-ray Emission

21


X ray emission energy jumps

X-ray Emission Energy Jumps

Emission

Excitation

Emission

22


X ray emission energy jumps1

X-ray Emission Energy Jumps

3d

3p

3s

2p

2s

1s

23


X ray emission spectroscopy

X-ray Emission Spectroscopy

X-ray emission spectrum of a Ni compound the exact position and intensity of the peaks can give information about the oxidation state and bonding

24


Production of x radiation in an x ray tube

Production of X-radiation in an X-ray Tube

High voltage extracts electrons from the anode and accelerates them towards the metal cathode

These high energy collisions eject electrons from inner atomic orbitals of the metal

High Voltage ~100,000 V

_

+

e-

X-radiation

Frequency depends on target metal

Metal Target


Production of x radiation in an x ray tube1

Production of X-radiation in an X-ray Tube

26


X ray tube

X-ray Tube

27


Production of x radiation in an x ray tube2

Production of X-radiation in an X-ray Tube

.

.

.

.

.

.

.

.

.

.

.

.

High energy electron after collision with metal atom in the target

High energy electron accelerated by voltage

e-

e-

e-

.

Inner shell electron ejected from the metal atom in the target

.

.

.

.

28


Production of x radiation in an x ray tube3

Production of X-radiation in an X-ray Tube

.

.

.

.

.

.

.

.

.

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EX-ray = hn = DEelectron

29


X ray fluorescence

X-ray Fluorescence

AtomicFluorescence

Excitation by X-rays ejects electrons from inner orbitals of atoms

Electrons from higher orbitals jump back to fill vacancies

Emission of fluorescence X-rays occurs

Results in Stokes shift to longer wavelength (lower energy since EFluorescence <EExcitation).

EExcitation = hnEx

e-

KE = 1/2mv2

EFluorescence = hnFl

e-

e-

30


X ray fluorescence instrument

X-ray Fluorescence Instrument

X-ray Excitation Source

Monochrometer

X-ray Tube

_

e-

+

Detector

EExcitation = hnEx

X-ray Emission

EFluorescence = hnFl

Sample


X ray fluorescence spectrometer

X-ray Fluorescence Spectrometer

32


X ray fluorescence analysis

X-ray Fluorescence Analysis

  • The fluorescence frequencies can be used to identify the elements in the sample

  • The intensity of the fluorescent X-ray beam is used to determine the concentration of specific elements using callibration standards


Spectroscopic analysis part 7 x ray analysis methods

Thank You for your Attention !


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