Charged particle interaction with matter

CHARGED PARTICLE
INTERACTION WITH MATTER
Sabari Kumar P
M.Sc. Radiation Physics

OUTLINE
Introduction
Heavy charged particle interaction with matter
Neutron Interaction
Proton Interaction
 Heavy Ion Interaction (Carbon Ion)
Light charged particle Interaction with matter
(Electron Interaction)
Summary

 How uncharged particle interacts, like wise charged particle can
also interact with matter
 Charged particle interaction mediated by Columbic forces
Interaction may happen between Charged particle and Orbital
electron (Ionization & Excitation) & Charged particle and Atomic
Nuclei (Radiative Energy Loss)
 Sometimes, Charged Particle interaction causes nuclear reactions
Ex: Proton interacts with Tissues and emits 11C, 13 N, and 15O
(Short lived Isotopes)
Depends upon mass, charged particles becomes Heavy and Light ones
Charged Particle interaction mainly classified into two types:
Elastic collisions (total K.E before = after interaction)
Inelastic collisions (some part of K.E used up)

Force proportional to Charge of the Particles
Force inversely proportional to distance between particles
Equation:
k q1 q2
F = ------------
r2
- +
F = Coulomb force
q’s = charges of the two particles
k = constant
r = distance between objects
COULOMB FORCE

HEAVY CHARGED PARTICLE INTERACTION
M
Q’
Q
x
Fyr
Fx Fx
ν
bE
+Ze
-e
θ
Alpha, Proton, Neutron and Deuteron are comes into Heavy Particles
 Even Neutron does not have any charge, because of its Heavy mass it
comes under this classification
 Here the charged particle in the sense, heavy charged one

 Consider a particle of mass M, moving with a velocity ν from
point M to Q’
Here Particle mass > Electron mass m0
 By applying Coulomb forces, Momentum imparted on electron
the energy lost by charged particle becomes,
Where z = Atomic Number
r0 = e2/m0c2 Classical radius of electron ( 2.818 x 10-13 m)
m0 = Rest Mass of Electron
c = Light Velocity (3x10-8m/sec)
ν = Electron Velocity
b = Impact parameter(2ze2/pv) ( p - Momentum)
E= Kinetic Energy of Charged Particle ( ½ mν2)
m = Mass of Charged Particle
E
m
.
b
cmrz
)b(dE 22
4
0
2
0
2



Case (1): dE(b)  1/E
High energy and high velocity Particle  Less energy transfer
(Less time only Charged Particle will be in region of electron)
Case (2): dE(b)  1/b2
b – Impact parameter ( The distance of closest approach between the
moving charged particle and the electron)
1. b>> atomic radius
 Energy transfer is very less
 Transferred energy << binding energy of electron
 such collisions are mostly elastic in nature
2. b> atomic radius
Energy transfer is small but high compared to earlier
Transferred energy ≤ binding energy of electron
 Ionization or excitation can cause
 generally called as Distant or soft collisions

3. b=atomic radius
 Considerable energy transfer occurs
 Transferred energy ≥ Binding energy of electron
 may cause δ – ray production
 called as Hard or close collisions
4. b< atomic radius
 Interaction between charged particle and nuclei
becomes more probable
 Causes bremsstrahlung photon generation
Note: Bremsstrahlung probability is very less in the case of heavy charged
particle due their heavy mass (  1/M2 )
 Impact parameter concludes that :
dE(b) =  for b = 0 large energy transfers in less interactions
dE(b) = 0 for b= small energy transfers in more interaction

Charged Particle randomly scattered
 chance to encounter All impacts (Near to far)
 The total energy loss of charged particle in a distance of dx becomes
 - ν/c of charged particle
Ne – No. of electrons per gram(N0.Z/A)
 At higher b values, the energy exchange insufficient to overcome the
binding energy of electrons
 In this case, electrons will undergo to excitation instead of Ionization
)]
b
b
[ln(
cmrz
.N4
dx
dE
min
max
2
2
0
2
0
2
e



To handle this situation, a semi empirical quantity “I” called Mean
Excitation energy of the atom is introduced
 I- value estimation is discussed by Berger and Seltzer
 The calculation of ‘I’ values are quite complex and theoretical values
are available for few elements.
I Value =
After including the Mean excitation energy ‘I’ , relativistic effects and
Quantum mechanics ,
the energy loss equation becomes,
This is known as the Bethe-Bloch equation





i
i2
2
22
0
2
2
0
2
e
2
0 ]
Z
c
)1(I
cm2
[ln
cmZ
Nr4
dx
dE
13Z8.71Z,52.8
13Z211.7ZeV,11.2
1Z19.0eV,




The (dE/dx) amount of energy lost per unit length along the track of
the particle which is called “Stopping power” . This (dE/dx) excludes
the binding energy of electron.
Stopping power (S.P) = dE/dx
Units : MeV/cm
 If ρ is the density of the medium, then the ratio of energy loss and
density is called “Mass Stopping Power”
Mass Stopping Power (S.P)m =(S.P)/ρ = 1/ρ (dE/dx)
Units : MeV.cm2/g
 From the above equation, we can conclude that
(S.P)  1/2  (S.P)  C2/ν2
As velocity of particle decreases, the energy lost rate increases
and does more ionization and more absorbed dose
STOPPING POWER

Useful quantity because it express the rate of energy loss of the
charged particle per g/cm2 of the medium traversed
Mass Stopping Power does not differ greatly for materials with similar
atomic composition (primarily light elements)
For 10 MeV protons ,
Mass Stopping Power of H2O is 45.9 MeV cm2/g
Mass Stopping Power of Pb (Z=82) is 17.5 cm2/g
Heavy elements are less efficient on a g/cm2 basis for slowing down
heavy charged particles (many of their electrons are too tightly bound
in the inner shells to participate effectively in the absorption of
energy)
STOPPING POWER Contd..

Mean Excitation Energy:
The I – value dependence of Energy lost is logarithmic which gives
that small uncertainty gives large variation in energy lost.
When Material is compound or Mixture, the I values calculated by
adding separate contribution from the individual components.
n . ln I compound = Ʃ N . Z . ln I individual
Ex: H2O Mean Excitation Energy Calculation
H (Z=1) , IH = 19.0eV ; O(Z=8), IO = 11.2+11.7 x 8 = 104.8eV
ln Iwater = (Ʃ N.Z. ln I )/n = NH . ZH ln (IH)/n + NO . ZO ln (IO)/n
= [2 x 1 x ln ( 19.0)] x 1/10 + [1 x 8 x ln (104.8)] x 1/10
ln Iwater = 4.312  Iwater = 74.6eV

SHELL CORRECTION:
When velocity of the passing particle ceases to be much greater than
that of the atomic electrons in the stopping medium, the mass-collision
stopping power is over-estimated
Since K-shell electrons have the highest velocities, they are the first to
be affected by insufficient particle velocity, the slower L-shell electrons
are next, and so on
 Shell Correction which gives that the electrons which do not fully
participate in ionization or excitation.
If charged particle velocity > bounded electron velocity
 No need of shell correction
If charged particle velocity = bounded electron velocity
 Becomes important
As Z increases, the magnitude of Shell correction also increases.
But difficult to evaluate. That’s why, it have omitted ( 2% error)

POLARIZATION CORRECTION:
The passage of a charged particle through a medium polarizes the
atoms of the medium.
The medium polarization screens the electric field of the charged
particle from the distant atoms, thus reducing the Stopping Power.
This effect depends on the number of atoms polarizing per unit
volume ( Density ) Hence it is called density effect.
This is important when relativistic effects increases.
The effect is negligible in Protons below about 1000MeV.
For electrons at low energies (1 MeV), this correction will be needed.

RANGE:
The range is defined as the distance of
charged particle travels before it is
coming to rest.
The thickness of the medium needed
for the entire energy absorption of a
particle is called the Range.
Reciprocal of S.P gives the distance
travelled per unit energy loss.
cm/eV
Since, Alpha particles are very heavy in
mass and double charged, they wont
acquire high velocities even at high
energies. So, they have very short range.

E
0 P.S
dE
R

Neutron Interaction
Interaction of neutrons with matter do not show smooth variations
with energy and atomic number which characterize most of the
interactions of photons with matter.
 Neutrons essentially interacts with the atomic nucleus
Neutron produces wide range of recoil nuclei and subatomic particles
as well as photons which undergo diff. type of interactions
Different types of interaction may possible :
Elastic collisions
Inelastic collisions
Non-elastic collisions
 Capture Process
 Spallation

Simplest process of neutron interaction with atomic nucleus
Neutron deflected with energy loss which is transferred to nucleus
 Energy transfer (Etr) becomes,
En = Neutron Energy
Ma = Nucleus Mass
m = Neutron Mass
θ= Recoil angle
Energy transferred to nucleus increases in case of less mass of nucleus
Hydrogen is good for stopping neutrons
 The reaction is represented symbolically 1H(n,n)1H
Elastic collision is important at low neutron energies (few MeV)
and not effective above 150 MeV


 2
2
a
a
ntr cos
)mM(
mM4
EE
Elastic collision

Inelastic collisions:
The word Inelastic is specially reserved for reactions in which a
neutron is the product particle as well as the incident particle
Incident Neutron momentarily captured by targeted nucleus
 Neutron re-emits with less energy
 Nucleus left in excited state
Nucleus relaxes by emitting charged particle or γ-rays
Ex: 16O(n , n’) 16O* with 6.1 MeV γ-ray

Nonelastic Collision:
If the particle resulting from the Inelastic interaction is not a neutron,
then Non-Elastic term is used
Ex: 16O(n,α)13C
In biologically important elements C, N and O, inelastic and Nonelastic
collision processes usually have energy thresholds in the range of
4 -12MeV
Capture Process:
Thermal neutrons with an energy of about 0.025eV are captured by
nuclei (under thermal equilibrium conditions)
This interaction cross section  1/ neutron energy
Ex: 1H(n,γ)2H – γ energy is 2.2 MeV
14N(n,p)14C – p energy is 0.6MeV

Spallation:
In this interaction, the neutron
causes the nuclear fragmentation,
several particles and nuclear fragments
being ejected
 Interaction becomes significant
above 20MeV

Interaction Coefficient:
Most useful interaction coefficient in neutron dosimetry is the Mass
Energy Transfer Coefficient (μtr/ρ)
From this one can calculate Kerma ( Energy transfer Coefficient x
energy fluence) a measure of a neutron radiation field
In neutron interactions kerma is equal to absorbed dose because of
small charged particle range
If ‘σ’ is the cross section for a particular neutron interaction with an
atom of mass M , then
Mass Attenuation Coefficient (μ/ρ) = NA . (σ/M)
Mass Energy Transfer Coefficient (μtr/ρ) = NA . (σ/M) . (Etr/EN)
Here Etr= Mean energy transfer b/w Neutron and charged particle
EN = Neutron Energy
The total mass energy transfer coefficient is sum of individuals

Relative Importance of Neutron interaction process
in H, C, N and O:
Soft tissues are mainly composed of the elements H, C, N and O
When Neutron interaction happens, Elastic scattering by H becomes
predominant between 100eV and 20MeV
 1H(n,n)1H reactions accounts for 97 % at 10KeV of neutron energy
87% at 8MeV of neutron energy
70% at 18MeV of neutron energy
The elastic scattering indeed by O, C, and N respectively above 10MeV
The range of charged particle released by neutrons even of 20MeV
will be very small

Linear Energy Transfer
Specific Ionization IS = SC/W
where W – Avg. energy for ionization
Sc = Collisional stopping power
Specific Ionization (No. of ions formed per unit length of particle track)
consider only mean ionization by means of energy transferred
But energy transfer may also occur to the medium by excitation
A unit to account for all energy liberated along the path of ionizing
particle is Linear Energy Transfer (LET)
LET is the energy released per micron medium along the track of any
ionizing particle
LET  Q2/V2
Slow moving and high charged particle  High LET(KeV/μm)
Fast moving and low charged particle  Low LET(KeV/μm)

LET is not a constant due to continuous decrease of particle velocity
through matter. For each interaction of particle with matter, the LET
increases along path length
A very drastic increase occurs in LET value, before the particle comes
to rest. This increase (Peak) in rate of dissipation is called Bragg Peak
It is a plot of LET v/s distance as a particle slows down
When heavy particle slows down in a medium, the rate of energy loss
will reach a peak towards the end of the track. As the particle slows
down, it captures electron, which reduces its charge and hence reduces
its energy
Particle Charge Energy LET (keV/μm)
Proton +1 Small 92
Proton +1 2MeV 16
Alpha +2 Small 260
Alpha +2 5MeV 95

Proton Interaction
Proton interacts with matter as
 atomic electrons and nuclei through coulomb forces.
 Rare collisions with nuclei results nuclear reactions
This interaction mediated by Coulomb force
 Inelastic collisions with atomic electrons and nuclei
Elastic Scattering
Due to heavy mass, as like electrons, proton can’t scatter
Scattering through small angle possible which results sharp lateral
distribution
Mass Stopping Power is greater in Low Z materials than high Z
materials
Low Z materials are more effective in slowing down protons
In Scattering foil design, for low energy loss and high scattering of
proton beam, High Z materials used
Head on collisions with nuclei results nuclear reactions (generates
protons, neutrons and some cases Alpha particles (11C, 13N and 15O)

Bragg Peak & Stopping Power curve of Proton Beam:
100MeV Proton Beam

Heavy Ion Interaction
In the same way how proton interacts with matter, as like Heavy Ions
can also interacts and deliver dose
From 2(He) to 18(Ar) elements are considered as Heavy ions
The depth dose curve of Heavy Ion beam in water looks likes Proton
Beam curve that has a sharp Bragg Peak near region where primary
particles stop

Interaction of Heavy ions have distinct physical characteristic when
compared to Proton interaction
In proton interacts, the incident particle interacts with target nuclei
and produce low energy protons or heavy ions
When heavy ions pass through the medium, they produce nuclei
fragmented from the projectile and the target nuclei
 The nuclei produced by fragmentation have approximately the same
velocity as the incident heavy ions and reach deeper regions than those
where the incident particles stop
Finally different energy distributions presents by fragmentation of
projectiles and targets (Can observe in Bragg peak tail at distal end)
The energy range used in Heavy ion beam ( Carbon ) around
80 – 400AMeV

 The Reaction between Heavy Ion and target elements and energy
released from secondary particles such as:
a + X ------>Y + b
Q=(ma + mb - mY – mb)2
TY = Ta + Q – Tb
Here a – Incident Ion
X- Target
Y & b – Product Particles
Q - Angle of incident ion
Ta – Incident Ion Energy
Tx – Target particle energy
Ty & Tb – Product particle energy
 
by
5.0
aayyby
2
aba
5.0
aba5.0
b
mm
T)mm(Qm)(mmcosTmm(cos)Tmm(
T




Reaction products range at maximum energy (C - 100MeV & 00 Scatter)

dE/dX curve w.r.t depth of secondary particles – C - ion Incident

Some Reactions causes that
generation of neutrons while
carbon interacts with tissue
 To analyze the tail region, the
reaction rate is the good parameter
such as:
Here,
N = ρ.NA/M
σ = Cross Section
 = No. of C ‘s/sec/m2



1
2
E
E
1223
)scm()cm()cm(NRate

Electron Interaction with Matter
When electron passes near the electric field of another electron or
that of a nucleus, it undergo scattering and changes its direction
The energy loss and the change of direction by the travelling electron
may be small or large which depends on collision
Energy loss can be significant, when electron-electron collision
happens
Direction change can be significant, when electron – nucleus field
interaction happens
Finally, electron interaction with matter causes two types of energy
losses
Collisional or Ionization loss
Radiative loss

Collisional Loss:
Important mechanism of energy loss of charged particles to make
ionization(Removal of bounded electron) and excitation(Lift of electron
to higher energy orbital) in matter
Electron – Electron collision may result large energy loss with marked
direction change
 Electron energy loss becomes,
Here Ne = No. of electrons per gram
E = Kinetic energy of the electron
I = Mean excitation energy of matter
μ0 = m0C2 (Rest mass energy of electron)
δ = Density correction
 = ν/C





















 2
2
0
2
00
2
2
0
0
2
2
0
e
2
0 1
)E(
n/)E2(8/E
I2
)2E(E
lnNr2
dx
dE1
S

Density Correction:
Interaction with distant electrons will be influenced by the electrons in
the intervening atoms
This results polarization of matters that means reduces electric field of
the incident electron. Finally, Energy loss of electron will reduce
The density effect is small in all materials for electron energies below
1MeV, but gradually increases up to 20% at 100MeV
S.P value:
 If the electron energy is low
 S.P value becomes very high
 As electron energy increases,
S.P rapidly decreases to minimum
and gain gradually increases
(due to insufficient electron energy
of electron)

I value:
In high Z medium, the electrons are bounded, so less ionization will
cause which indicates that high I value
S.P is low for high medium  very high I values
β value:
From the S.P equation,
S.P  1/β2
For the energies above 100 KeV, β closes to 1.0
This makes, the outside the bracket constant

Radiative Loss:
When the electron passes close to the coulomb field of a nucleus of
an atom, the electron decelerates and loss energy by releasing radiation
in the form of X-rays
These x-rays have continuum of energies and hence called continuous
white X rays (or) Bremsstrahlung ( Braking) X – rays
The fraction of the electron energy lost in this process depends on
how close the electron comes to the nuclei.
M
Q’
Q
x
Fyr
Fx Fx
ν
bE
-Ze
Ze
θ

Consider
Mass of electron M Charge -ze
Mass of Nucleus MN Charge Ze
Electrostatic force on electron = KzZe2/r2
Acceleration due to force becomes = KzZe2/r2M
If M << MN
 nucleus won’t move, but electron deflects from its path (MQ’ -->MQ)
Decelerated particle emits Radiation
Radiative Energy  1/(Electron Acceleration)2
Radiative Energy  1/[zZe2/M]2
Which implies Radiative Loss  Z2
Radiative Loss  1/M2
Deceleration of electron results the radiation, hence Bremsstrahlung

Rate of Energy Loss becomes
Finally, the Radiative energy loss  atomic number of medium
and also slowly with the energy of the electron
This table gives
S.P values of electron
Energies in water

















3
1)E(2
ln
137
ZEN
r4
dx
dE1
P.S
0
0e2
0
Energy
(S.Pcol)
Mev cm2/g
(S.Prad)
Mev cm2/g
Total S.P
MeV cm2/g
10KeV 2.256 E+1 3.898E-03 2.257 E+1
50KeV 6.603 4.031 E-03 6.607
100KeV 4.115 4.228E-03 4.120
500KeV 2.034 7.257E-07 2.041
1MeV 1.849 1.280E-02 1.862
1.25MeV 1.829 1.600E-02 1.845
5MeV 1.892 7.917E-02 1.971
10MeV 1.968 1.814E-01 2.149
25MeV 2.070 5.277E-01 2.598

Stopping Power
Total Stopping Power (dE/dx)total can be divided into Collisional
component S.Pcol[dE/dx]col and Radiative component S.Prad[dE/dx]rad
For low energy electrons, Collision Process dominates
 Entire energy loss S.Pcol
For higher energy electrons with high Z materials,
Radiative Process becomes dominates
 Max. energy loss S.Prad
If electron energies > 1-2MeV
 S.Pcol becomes constant
radcoltotal
radcoltotal
dx
dE
dx
dE
dx
dE
P.SP.SP.S




















Rates of energy loss of electrons in matter

Bremsstrahlung Yield:
 Consider E0 initial energy of electron set in motion in the medium.
The instantaneous energy loss of electron Energy loss E =Erad+Ecol
Total radiated energy,
The fraction of the radiated energy,
This fraction is called Bremsstrahlung Yield.
The Stopping power is proportional to E and Z2.
The path length increases with E, but decreases with Z
 Thus, the total bremsstrahlung yield  E2.Z [(E.Z2).(E/Z)]
E
)E(S
)E(S
E
total
rad
rad  E
)E(S
)E(S
E
total
col
col 
 
0E
0 total
rad
dE
)E(P.S
)E(P.S
ergyRadiatedEn
dE
)E(P.S
)E(P.S
E
1
B
0E
0 total
rad
0
 

Angular Distribution of Bremsstrahlung:
It pointedly differ from low and high energy incident electrons
At low energies,
1. Max. intensity at an angle of 500 to 600
2. Forward intensity considerable small
3. Negligible in backward direction
At high energies,
1. Intensity peak towards forward
Energy
B Fraction
In Water In Air
10KeV - -
50KeV 0.0003 0.0004
100KeV 0.0006 0.0007
500KeV 0.0020 0.0022
1MeV 0.0036 0.0040
2MeV 0.0071 0.0078
5MeV 0.0190 0.0201
10MeV 0.0404 0.0412
50MeV 0.1910 0.1820

Range:
Thickness of medium to absorb entire electron energy is called Range
Electron range is not so well defined due to frequent scattering nature
Used in therapy to estimate electron beam penetration
Different methods are defined for electron range calculation
---CSDA (Continuous Slowing Down Approximation)
---Practical Range (Extrapolation Method)

In CSDA Method, all collisions are
assumed to involve very small energy
exchanges and it is an integration along
the actual paths followed by the
electron. The CSDA range is defined as
R0 (E0) = dE/(dE/dx)t
The convenient thumb rule that for
electron energies about 0.5MeV or
more the range in unit density material
is (in cm) about half the energy in MeV
RP = E/2
The average range also defined as the
depth at which the dose becomes 50%
of its maximum(R50)
Energy
Range(g/cm2)
In Water In Air
10KeV 0.0003 0.0003
50KeV 0.0049 0.0043
100KeV 0.0162 0.0143
500KeV 0.1989 0.1759
1MeV 0.4905 0.4359
2MeV 1.082 0.9720
5MeV 2.738 2.524
10MeV 5.191 4.917
50MeV 19.54 19.73
100MeV 31.73 32.47

In practical range method,
Extrapolated straight falling portion
of the depth dose curve on to the
bremsstrahlung tail
(from Berger – Seltzer relation)
RP = 0.5 – (EP)0-0.111
(from ICRU-NACP relation)
RP=0.22+1.98RP+0.0025RP
2
Here EP is the initial Electron Energy
Range can also calculate from S.P
data
Range = Energy/S.P
Range (R) =  EK/(S.P)tot dEK

Path Length:
The actual path followed by an electron in its travel through matter
gives path length of electron
The thickness of the absorber that the electron can just penetrate,
gives range of electron
Because of multiple scattering, there is considerable difference
between both concepts in case of low energy and high Z materials
 Path length can be observed in cloud chamber or in photographic
emulsions
 Range is an experimental concept and is usually measured
experimentally

Mean Stopping Power:
Consider electron with Ei initial energy with a range of R passing through
medium, if the electron beam is mono energetic,
Ei B is the bremsstrahlung energy loss
Ei-EiB is the deposited energy in the medium
The mean ionization stopping power becomes
If the electron spectrum is represented by d(E)/dE, then
R
)B1(E
)E(P.S i
i






 i
i
E
0
E
0
ion
i
dE.
dE
)E(d
dE).E(S.
dE
)E(d
)E(P.S

Restricted Stopping Power (LET):
S.P is used to characterize the rate at which the electrons lose energy
along track.
Another parameter like S.P is Linear Energy Transfer (LET) or Restricted
S.P
These are useful to know how much energy on the matter actually
deposited by charge particle in dosimetry
 Due to charged particle passage through medium, there may be chance
of δ-ray energy
This energy carried away is included in S.P but is exclude from R.S.P
 The R.S.P can be calculated by



















 









2
2
0
00
2
2
0
0
2
0
e
2
0 1
)E(
E
E
ln)E2(
2
E
E
I
)E)(2E(2
lnNr2L

Here  - Specified Energy to the secondary particle
The R.S.P values for  = 0.0001 to  = 0.1 for water for different
energies given in table
In S.P, not only primary particle track energy loss accounted but also
secondary electron track also consider. Hence, this is called Unrestricted
S.P (or) Total S.P
The restricted S.P is a part of contribution of collision even is that transfer
less that specific energy () to the secondary particle
The Small size of , the stricter to the secondary particle tracks
The higher value chosen makes Restricted S.P becomes close to Total S.P
Energy L0.0001 L0.001 L0.01 L0.1
0.1MeV 2.471 3.106 3.735
0.2MeV 1.632 2.037 2.436 2.793
1MeV 1.034 1.256 1.477 1.697
10MeV 1.028 1.227 1.426 1.625
100MeV 1.054 1.249 1.445 1.640

S.No Uncharged Particle Interaction Charged Particle Interaction
1 Interacts with matter gives rise to
the release of charged particles
Transfer their energy to the
medium through which they pass
2 Small no. of interactions with
large energy losses
Large no. of interactions with small
energy losses
3 Can’t interact with electron or
nucleus by long range coulomb
force
(impact parameter -10-11cm)
Can interact with an atom even
when impact parameter is larger
than this value by 3 or 4 orders of
magnitude
4 Less interaction cross-section More interaction cross-section
5 Zero rest mass of photon Non zero rest mass of particle
6 Photon can’t decelerates Charged can decelerates
7 Travels with light velocity Velocity comparable with respect
to light velocity
8 Energy loss per unit distance
can’t determined that’s why no
meaning of Stopping Power and
Range
Definite Energy loss per unit
distance can determined which
makes more importance of
Stopping Power and Range
SUMMARY

Charged particle interaction with matter

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