This document provides an overview of photoacoustic spectroscopy (PAS). It discusses the history of PAS, which was discovered by Alexander Graham Bell in 1880. PAS allows for absorption spectroscopy of opaque and scattering samples by detecting the acoustic signal generated from the sample's absorption of modulated light. The document describes the basic photoacoustic effect, conventional PAS setups, applications like surface studies and blood analysis, and examples of PAS spectra. It establishes PAS as a non-destructive technique for obtaining optical absorption data from solids, semisolids, and turbid liquids that conventional spectroscopy cannot analyze due to light scattering.
A presentation on Photoacoustic Spectroscopy by Deepak Rajput, UT Space Institute, TN, USA.
This presentation was made as a course requirement at the University of Tennessee Space Institute at Tullahoma.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
A presentation on Photoacoustic Spectroscopy by Deepak Rajput, UT Space Institute, TN, USA.
This presentation was made as a course requirement at the University of Tennessee Space Institute at Tullahoma.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
Basic operating principle and instrumentation of photo-luminescence technique. Brief description about interpretation of a photo-luminescence spectrum. Applications, advantages and disadvantages of photo-luminescence.
Raman Spectroscopy - Principle, Criteria, Instrumentation and ApplicationsPrabha Nagarajan
Basic principle of Raman scattering- Difference between Rayleigh and Raman Scattering- Major criteria for Raman active in compounds,-Stroke's lines and Anti-stoke lines- Difference and between IR and Raman spectroscopy- Wide applications of Raman spectroscopy.
CHECKOUT THIS NEW WEB BROWSER :
https://www.entireweb.com/?a=618b79ed612f3
It is a multi-element analysis technique that will separate a sample into its constituent atoms and ions and excite it to a higher energy level.
Cause them to emit light with a distinct wavelength, which will be analyzed.
X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for chemical analysis (ESCA) is used to investigate the chemistry at the surface of the samples. The basic mechanism behind an XPS instrument is that the photons of a specific energy are used to excite the electronic states of atoms at and just below the surface of the sample.
There are several areas suited to measurement by XPS:
1. Elemental composition
2. Empirical formula determination
3. Chemical state
4. Electronic state
5. Binding energy
6. Layer thickness in the upper portion of surfaces
XPS has many advantages, such as it is is good for identifying all but two elements, identifying the chemical state on surfaces, and is good with quantitative analysis. XPS is capable of detecting the difference in the chemical state between samples. XPS is also able to differentiate between oxidations states of molecules.
XPS has also some limitations, for instance, samples for XPS must be compatible with the ultra high vacuum environment. XPS is limited to measurements of elements having atomic numbers of 3 or greater, making it unable to detect hydrogen or helium. XPS spectra also take a long time to obtain. The use of a monochromator can also reduce the time per experiment.
Basic operating principle and instrumentation of photo-luminescence technique. Brief description about interpretation of a photo-luminescence spectrum. Applications, advantages and disadvantages of photo-luminescence.
Raman Spectroscopy - Principle, Criteria, Instrumentation and ApplicationsPrabha Nagarajan
Basic principle of Raman scattering- Difference between Rayleigh and Raman Scattering- Major criteria for Raman active in compounds,-Stroke's lines and Anti-stoke lines- Difference and between IR and Raman spectroscopy- Wide applications of Raman spectroscopy.
CHECKOUT THIS NEW WEB BROWSER :
https://www.entireweb.com/?a=618b79ed612f3
It is a multi-element analysis technique that will separate a sample into its constituent atoms and ions and excite it to a higher energy level.
Cause them to emit light with a distinct wavelength, which will be analyzed.
X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for chemical analysis (ESCA) is used to investigate the chemistry at the surface of the samples. The basic mechanism behind an XPS instrument is that the photons of a specific energy are used to excite the electronic states of atoms at and just below the surface of the sample.
There are several areas suited to measurement by XPS:
1. Elemental composition
2. Empirical formula determination
3. Chemical state
4. Electronic state
5. Binding energy
6. Layer thickness in the upper portion of surfaces
XPS has many advantages, such as it is is good for identifying all but two elements, identifying the chemical state on surfaces, and is good with quantitative analysis. XPS is capable of detecting the difference in the chemical state between samples. XPS is also able to differentiate between oxidations states of molecules.
XPS has also some limitations, for instance, samples for XPS must be compatible with the ultra high vacuum environment. XPS is limited to measurements of elements having atomic numbers of 3 or greater, making it unable to detect hydrogen or helium. XPS spectra also take a long time to obtain. The use of a monochromator can also reduce the time per experiment.
Judd-Ofelt Theory: Principles and PracticesBrian Walsh
Presented at The International School of Atomic and Molecular Spectroscopy (Erice. Italy, June 2005)
Publication Reference: B.M. Walsh, “Judd-Ofelt Theory: Principles and Practices”, in Advances in Spectroscopy for Lasers and Sensing, B. Di Bartolo and O. Forte, eds. (Springer, Netherlands, 2006), pp. 403-433.
An Infrared spectrum represents a fingerprint of a sample with absorption peaks which correspond to the frequencies of vibrations between the bonds of the atoms making up the material-Because each different material is a unique combination of atoms, no two compounds produce the exact same spectrum, therefore IR can result in a unique identification of every different kind of material!
A short lecture about Atomic Spectroscopy: Flame Photometry, Atomic Absorption, and Atomic Emission with Coupled Plasma (FP, AA and ICP-AES). Presented at 28.03.2011, Faculty of Agriculture, Hebrew University of Jerusalem, by Vasiliy Rosen, M.Sc.
Atomic spectroscopy plays a major role as the basis of a wide range of analytical techniques that contribute data on elemental concentrations and isotope ratios .These analytical data provide the raw material on which progress in geochemistry depends.
The main advantages of AAS & AES are that it is relatively inexpensive and easy to use, while still offering high throughput, quantitative analysis of the metal content of solids or liquids. This makes it suitable for use in a wide range of applications.
Atomic Absorption Spectroscopy RESEARCH TECHNIQUES IN ANIMAL NUTRITION.pptxDr. Rahul kumar Dangi
A simple total ash determination provides very little information about the exact mineral profile of the feed/food. Analytical techniques involving spectroscopy are generally used to obtain the macro and micro mineral contents except the phosphorus.
Atomic absorption spectroscopy is a very common technique for detecting metals and metalloids.
It is very reliable and simple to use.
It can analyze over 62 elements.
It also measures the concentration of metals in the sample.
First AAS was built by CSIRO scientist Alan Walsh in 1954
The technique makes use of the atomic absorption spectrum of a sample in order to assess the concentration of specific analyte within it. It requires standards with known analyte content to establish the relation between the measured absorbance and the analyte concentration and relies therefore on the Beer-Lambert law.
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
For instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromator
Detector
Recorder
VFor instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments.
Any AAS instrumentation has the following types of components:-
Atomization
Hollow cathode lamp
Monochromato
Spectroscopy using spectrophotometers of different types like: U.V, Mass Spectrophotometer, absorption , Emission, Nuclear magnetic resonance and X-rays Spectrophotometer
2. History
Photoacoustic effect discovered by Alexander Grahm
Bell in 1880
Bell found that when light was focused on to thin
diaphragm, sound was emitted
Bell also studied the sounds produced by the irradiation
of various solid samples in a brass cavity sealed with a
glass window
4. Introduction
PAS or Optoacoustic spectroscopy was developed
in 1973 which provides UV, Visible and IR absorption
spectra of solids, semisolids and turbid liquids
Obtaining of spectra for above kind of samples by
ordinary methods is usually difficult because of light
scattering and reflection
It is non-destructive technique
Minimal or no sample preparation
5. Applied for opaque and scattering samples
Used for qualitative and quantitative experiments
Used to detect defects on the surface of thin films
6. The Photoacoustic effect
PAS is based upon a light absorption effect
In PAS the gas to be measured is irradiated by a
chopped beam of light of a pre-selected wavelength
The gas molecules absorb some of the light energy and
convert it in to an acoustic signal which is detected by a
microphone
If the frequency of the light coincides with an absorption
band of the gas in the cell, then the gas molecules will
absorb part of the light
7. The higher the concentration of gas in the cell, the more
light will be absorbed
As the gas absorbs energy, it is heated and therefore
expands and causes a pressure rise
As the light is chopped, the pressure will alternately
increase or decrease and an acoustic signal is thus
generated
Only the absorbed light is converted to sound
The acoustic signal is detected by microphone
The electrical output signals from the microphone are
added in an amplifier before they are processed
8. Photoacoustic effect in solids
In PAS studies of solids, the PAS effect is observed by
from periodic heat flow from the solid to the surrounding
gas
The periodic heat flow produces pressure fluctuation in
the gas of the cell and are detected by the microphone
The power of resulting sound is directly related to the
extent of absorption of light by solid
The analog signal from microphone recorded as a
function of wavelength of incident light
The radiation reflected or scattered by the sample has
no effect on microphone and thus does not interfere
11. Instruments
A single beam PAS the spectrum from the lamp is first
recorded digitally followed by the spectrum for the
sample
The stored lamp data then used to correct the output
from the sample for variations in the lamp output as a
function of wavelength
Double-beam instrument is equipped with a pair of
matched cells (and transducers), one contains a sample
and the other reference material such as finely divided
carbon
12. Applications
Bulk studies :
- PAS provide optical data for solids which are not
highly reflective, highly opaque or highly scattering (e.g.
Insulator, semiconductor & metallic systems)
-Many solid & semi solid biological systems can be
studied by PAS
Surface studies
De-excitation studies
13. UV/visible PA spectroscopy
PAS permits spectroscopic
studies of blood without
separation of blood cells,
protein & lipid molecules
The whole blood does not
yield satisfactory spectra by
conventional spectroscopy
because of highly scattering
properties of large molecules
PAS spectra of
smears of blood and
blood components
14. Non-biological studies
Spectrum: (a) PAS of Cr2O3
powder in the region 200-900
nm
(b) Optical absorption
spectrum on a 4µ thick Cr2O3
crystal
(c) Diffuse reflectance
spectrum on Cr2O3 powder
The two crystal field bands of
Cr3+ ion at 600 & 460 nm are
clearly resolved in PA
spectrum as they are in
absorption spectrum of Cr2O3
crystal
PAS spectra of
Cr2O3
15. Surface studies
Adsorbed & chemisorbed molecular
species on the surfaces of metals,
semiconductors and insulators can
be studied by PAS
PAS offers a simple & highly
sensitive means for performing nondestructive compound identification
directly on the TLC plates
Conventional spectroscopic
techniques are unsuitable because of
the opacity & light scattering
properties of silica gel adsorbent on
the TLC plates
The compounds are:
(A) p-nitroaniline
(B) benzylidene
acetone
(C) salicylaldehyde
(D) 1-tetralone and
16. De-excitation (Fluorescent)studies
PA effect measures non-radiative
de-excitation processes in a
system after it has been optically
excited
This selective PAS technique
applied to study of florescent (or
phosphorescent) &
photosensitive materials
Fluorescent Ho2O3: Ho3+ have
strong fluorescent energy levels
& these tend to de-excite through
the emission of photon rather
than phonon or heat excitation
PAS spectra of Ho2O3
17. References
1. Principles of Instrumental Analysis, 5th Edn., Skoog and
West
2. Photoacoustics and Photoacoustic Spectroscopy, Allan
Rosencwaig (Chemical Analysis , Vol.57)
3. Rosencwaig A. Photoacoustic Spectroscopy: A New
Tool for Investigation of Solids, Anal. Chem. 1975,
47(6), 592 A-604 A.