Ion cyclotron resonance spectroscopy and photo acoustic spectroscopy

Offering my
humble pranams
at swami’s lotus
feet..,
1

SRISATHYASAIINSTITUTEOFHIGHERLEARNING(DEEMED UNIVERSITY)
PCHM-302
1. ION CYCLOTRON RESONANCE
SPECTROSCOPY
2. PHOTO ACOUSTIC SPECTROSCOPY
T. Manikantha
2nd M.Sc, chemistry
18107

1.Ion cyclotron resonance
spectroscopy:
1.INTRODUCTION
2.PRINCIPLE
3.INSTRUMENTATION
4.APPLICATIONS
3

INTRODUCTION:
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1.Mass spectrometry (MS) is an analytical technique that measures the
mass-to-charge ratio of ions.
2.In a typical MS procedure, a sample, which may be solid, liquid, or
gaseous, is ionized, for example by bombarding it with electrons. This may
cause some of the sample's molecules to break into charged fragments or
simply become charged without fragmenting.
3.These ions are then separated according to their mass-to-charge ratio, for
example by accelerating them and subjecting them to an electric or
magnetic field: ions of the same mass-to-charge ratio will undergo the same
amount of deflection.

MASS ANALYZER:
A “mass analyzer” is the heart of the mass spectrometer that takes ionized
masses and separates them based on charge to mass ratios and outputs
them to the detector where they are detected and later converted to a digital
output
Types of mass analyzers in MS:
1.Quadrupole mass analyzer
2.Time of flight mass analyzer(TOF)
3.Magnetic sector mass analyzer
4.Electrostatic sector mass analyzer
5.Quadrupole ion trap mass analyzer
6. “ION CYCLOTRON RESONANCE”

cyclotron:
1.cyclotron : A type of particle accelerator invented
by Ernest O. Lawrence in 1929–1930 at the
University of California, Berkeley, and patented in
1932.
2. Lawrence was awarded the Nobel prize in the
year 1939 in physics for this invention. .
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1. 1.Ion cyclotron resonance is the phenomenon related to the movement
of ions in a magnetic field.
2. 2.It is used for accelerating ions in a cyclotron for measuring the masses
of ionized analyte/s in mass spectrometry.
3.Cyclotron uses a magnet and voltage to accelerate charged particles
4. It is circular particle accelerator capable of generating particle energies
between 1MeV to more than 100 MeV
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Ion cyclotron
resonance

Construction:
This device has three main constructional
parts:
1. Large sized electromagnet to create
uniform magnetic field in between its face-
to-face placed magnetic opposite poles
2. Two low height hollow half cylinders
made of high conductive metals of
cyclotron are called “dees”
3. A high frequency alternating high voltage
source.
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Principle:
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1. Charged particle moving in normal / perpendicular to a
magnetic field experiences magnetic Lorentz force due to which
the particle moves in a circular path
2. Lorentz’s force is the basic principle of cyclotron
3. Conceptually this device is very simple but it has huge uses in
the field of engineering, physics and medicine.

WORKING:
1. When a positive ion of charge q and mass m is emitted from the source, it is
accelerated towards the Dee having a negative potential at that instant of time.
2. Due to the normal magnetic field, the ion experiences magnetic Lorentz
force and moves in a circular path
3. By the time the ion arrives at the gap between the Dees, the polarity of the
Dees gets reversed.
4. Hence the particle is once again accelerated and moves into the other Dee
with a greater velocity along a circle of greater radius.
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× Typical ICRS…,
Schwartz J C, Senko M W, Syka J E P. A two-
dimensional quadrupole ion trap mass spectrometer.
Journal of the American Society for Mass Spectrometry,
2002, 13(6): 659-669.

1.An ion in a static and uniform magnetic field will move in a circle due to the Lorentz
force. The angular frequency of this cyclotron motion for a given magnetic field
strength B is given by
where z is the number of positive or negative charges of the ion, e is the elementary
charge and m is the mass of the ion.An electric excitation signal having a frequency f
will therefore resonate with ions having a mass-to-charge ratio m/z given by
The circular motion may be superimposed with a uniform axial motion, resulting in a
helix, or with a uniform motion perpendicular to the field (e.g., in the presence of an
electrical or gravitational field) resulting in a cycloid.
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Resonating frequency:

Gaussian units
The above is for SI units. In some cases, the cyclotron frequency is
given in Gaussian units. In Gaussian units, the Lorentz force differs
by a factor of 1/c, the speed of light, which leads to:
For materials with little or no magnetism (i.e. μ ≈ 1) H=B, so we can
use the easily measured H instead of B:
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1.Maintaining a uniform magnetic field over a large area of the Dees
is difficult.
2.At high velocities, relativistic variation of mass of the particle
upsets the resonance condition.
3.At high frequencies, relativistic variation of mass of the electron is
appreciable
and hence electrons cannot be accelerated by cyclotron.
4.It cannot accelerate neutron, because neutron does not have any
charge.
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Limitations:

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APPLICATIONS:
1. Can be used to determine masses with high accuracy
2. ICR-MS is able to achieve higher levels of mass accuracy than
other forms of mass spectrometer, in part, because a
superconducting magnet is much more stable than radio-frequency
(RF) voltage..
3. This high resolution is also useful in studying large
macromolecules such as proteins with multiple charges, which can
be produced by electrospray ionization.
4. Cyclotrons can be used in particle therapy to treat cancer

On March 8, 2013, NASA released an article according to which ion cyclotron
waves were identified by its solar probe spacecraft called WIND as the main
cause for the heating of the solar wind as it rises from the sun's surface.
Before this discovery, it was unclear why the solar wind particles would heat up,
instead of cool down, when speeding away from the sun's surface.
The solar wind is a stream of charged particles released from the upper
atmosphere of the Sun, called the corona. This plasma mostly consists of
electrons, protons and alpha particles with kinetic energy between 0.5 and
10 Kev.
16

1. WIKI PEDIA
2. SLIDE SHARE. NET
3..Ion cyclotron resonance spectroscopy
J. D. BALDESCHWIELANEDR S. S. WOODGATE
( 1970) , vol-4.
4. Ion cyclotron resonance spectroscopy
J. L. BEAUCHAM (1971)
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References:

2. Photo acoustic spectroscopy
1.INTRODUCTION ( PA effect)
2.PRINCIPLE
3.PAC-GASES AND CONDENSED
SYSTEMS
4.APPLICATIONS
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INTRODUCTION:
1.The photoacoustic (PA) or opto acoustic (OA) effect, i.e. the generation of
acoustic waves due to the absorption of modulated electromagnetic waves.
2.The discovery of the photoacoustic effect dates to 1880 when Alexander
Graham Bell showed that thin discs emitted sound when exposed to a
beam of sunlight that was rapidly interrupted with a rotating slotted disk
3. This effect is weak; only a very small fraction (<1ppm) of the absorbed
optical energy is converted into acoustic energy.
4.In order to obtain this effect the light intensity must vary, either
periodically (modulated light) or as a single flash (pulsed light). 19

Jessica et al ,Published: March 21, 2019
https://doi.org/10.1371/journal.pone.0213625 21

PAC spectroscopy:
This spectroscopic technique can be broadly classified into two, i.e.; for gases and for
condensed medium.
PAC spectroscopy: GASES
1.According to the various gas laws, an increase in the temperature of the gas
leads to an increase in the pressure of an isochoric (constant-volume) sample.
2.If the incoming light is modulated — modulation frequencies can vary from single
to several thousand hertz — the gas pressure increases and decreases
accordingly, creating sound.
3. Varying the wavelength of the incoming light will change the amount of light
absorbed, the amount of pressure changes occurring, and the amount of sound
produced, and a spectrum of loudness versus wavelength can be produced.
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4.The laser beam is sent through the absorber cell.
5.If the laser is tuned to the absorbing molecular transition part of the
molecules in the lower level will be exited into upper level by collisions with
other atoms or molecules in the cell.
6. These exited molecules may transfer their excitation energy completely or
partly into translational, rotational, or vibration energy of the collision
partners. 23

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7.When the laser beam is chopped at frequencies Ω < 1/T, where T
is the mean relaxation time of the exited molecules, periodic
pressure variations appear in the absorption cell, which can be
detected with a sensitive microphone placed inside the cell.
8.The output signal S(volt) of the microphone is proportional to the
pressure change Δ P induced by the absorbed radiation power ΔW.
If saturation can be neglected, the absorbed energy per cycle is
given by

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absorbed energy is proportional to the density Ni [/cm3] of the
absorbing molecules in level ,the absorption cross section σik , the
absorption path length Δx, the cycle period Δt, and the incident
power PL. the signal decreases with increasing quantum efficiency
ηk, unless the fluorescence is absorbed inside the cell and
contributes to the temperature rise.

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Since the absorbed energy ΔW is transferred into kinetic or internal energy of all N
molecules per cm3 in the photoacoustic cell with the volume V, the temperature
rise ΔT is obtained from,
ΔW = ½ fVNkΔT
Where f is the number of degrees of freedom that are accessible for each of the N
molecules at temperature T[k]. If the chopping frequency of the laser is sufficiently
high, the heat transfer to the walls of the cell during the pressure rise time can be
neglected.
From the equation of state, we may obtain that
Δp = NkT = (2ΔW)/fv
The output signals from the microphone is then
Where the sensitivity Sm of the microphone not only depends on the
characteristics of the microphone but also on the geometry of photo-acoustic cell.

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PA spectroscopy(condensed matter)
The Gas-coupling method:
1.Use of gas-phase microphone for detecting PA signals in condensed matter
2. PA signal was generated by light beam incident on the condensed sample,
and the periodic heating of the gas at the irradiated surface of the sample
generated the acoustic wave, which was detected by the gas-phase
microphone.

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The periodic heating of the sample occurs in the “absorption length” μα of the
sample.
But only the heat within a diffusion length μs from the interface can
communicate with the gas and heat up a layer of gas of length μg (diffusion
length in gas) which expands periodically, producing acoustic waves.
‘Ds’ and ‘Dg’ are the thermal diffusivities in the sample and in the gas and
‘’f’’ is the modulation frequency of light beam

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LIMITATIONS:
1. Perfect implementation is available only for gaseous sample.
2. Photoacoustic spectroscopy can also be limited because laser
light is not very broad in bandwidth; the analyte molecule must
absorb some light from the source in order to be detectable.

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ADVANTAGES & APPLICATIONS:
1. These measurements are useful to determine certain properties of the
studied sample( eg. Absorption of excited states )
2.For example, in photoacoustic spectroscopy, the photoacoustic signal is
used to obtain the actual absorption of light in either opaque or transparent
objects.
3.It is useful for substances in extremely low concentrations, because very
strong pulses of light from a laser can be used to increase sensitivity and very
narrow wavelengths can be used for specificity.

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5.Analysis of textile dyes.
6.The photoacoustic effect is used to study biological samples such as blood,
skin, eye lenses, tumors, and drug-laced tissues.
7. Several studies are available in which photoacoustic spectroscopy has been
used to identify different types of bacteria.

1.WIKI PEDIA
2. SLIDE SHARE. NET
3.. Applications of photoacoustic sensing techniques
Andrew C. Tam
Rev. Mod. Phys. 58, 381 – Published 1 April 1986
4.Photoacoustic spectroscopy. New tool for investigation of solids
A. Rosencwaig
Analytical Chemistry 1975 47 (6), 592A-604a
DOI: 10.1021/ac60356a015
References:
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Let’s review
concepts…,
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Thanks!
Any questions???
You can find me at:
manikanthatumarada55@gmail.com
Linked in.com/tumarada manikanta
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Ion cyclotron resonance spectroscopy and photo acoustic spectroscopy

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