This document provides an overview of basic nuclear physics concepts. It discusses the structure of atoms including protons, neutrons, and electrons. It defines terms like atomic number, mass number, and isotopes. It explains concepts such as binding energy, radioactive decay modes (alpha, beta, gamma), activity, and half-life. Radioactive decay is described as the process by which unstable atoms emit particles or radiation to become more stable. Common decay types and their products are outlined.

1. Basics Of Nuclear Physics
By
Muhammad Zeeshan Khalid

2. The Atom
The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
2. Orbiting electrons.

3. The Atom
All matter is made up of elements (e.g. carbon,
hydrogen, etc.).
The smallest part of an element is called an atom.
Atom of different elements contain different numbers of
protons.
The mass of an atom is almost entirely due to the
number of protons and neutrons.

4. X A
Z
A = number of protons + number of neutrons
Z = number of protons
A – Z = number of neutrons
Number of neutrons = Mass Number – Atomic Number

5. Binding Energy
• The missing energy that keeps the nucleus together
1
1H
Mass Of Atom 1.007825 u
+ Mass of neutron +1.008665 u
__________________ __________
2
1H
Expected Mass of atom 2.016490 u
2
1H
 The mesasurd mass of = 2.014102 u
 So the difference is 0.002388 u
DE = (0.002388u)(931.48Mev / u) = 2.224Mev

6. CONCEPT OF BINDING ENERGY
The binding energy of an atom is the energy released as all the constituent
particles (n, p and e) come together FROM INFINITY under both the STRONG
force and the EM force.
The binding energy is something that is LOST from the atomic system. Thus it
is not something that the system possesses.

7. CALCULATION OF BINDING ENERGY
Total Energy Total Energy
(Zm Nm Zm ) c ( X ) c B E p n e N M A 2 .
+ + 2 º +
Z
( ) 2 ( )
2
( ( ))
( ) 2
B E m Nm Zm c M X c
2
= + + -
. Z
A
= + -
mass constituents - mass atom
c
Zm Nm M X c
H n Z
N
A
p n e Z
=

8. ANOTHER WAY OF VIEWING BINDING ENERGY
+
ATOM Constituents at infinity
The opposite way of seeing binding energy - is that if B.E.
(MeV) is put into the atom then there is just enough energy
available to split all the constituents of the atoms apart and get
them to rest at infinity.

9. SINGLE NEUTRON SEPARATION ENERGY
The same method can be used to easily compute the “Single Neutron
Separation Energy” – which is the energy required to “pull” a neutron out of the
nucleus.
( ) ( )
[ ( ) ( )] 2
S + M X c º M
X c +
m c
S X m X c
1
1
2 2
1
2 1
M M
N
A
N n Z
A
n Z
N n
A
N Z
A
n Z
= + -
-
-
-
-
Note we don’t have to measure Sn directly.

10. SINGLE PROTON SEPARATION ENERGY
The same clever strategy applies to finding the “Single Proton Separation
Energy” Sp. But note here there is a difference – we must be careful in
counting electron mass.
( ) ( 1 ) 2 2 2
S M X c2 M Y c m c m c 1
N p e
A
N Z
A
+ º - + +
p Z -
[ ( -
) ( )]
-
[ ( 1 ) ( )] 2
1 2
1
S = M Y + m + m -
M
X c
Y m X c
M M
1
N
A
N H Z
A
Z
N
A
N p e Z
A
p Z
= + -
-
-
= p S [Mass of Final Products – Mass of Initial atom] c2

12. THE FAMOUS B/A (binding energy per nucleon) CURVE

13. Isotopes
• Isotopes are variants of a particular chemical
element such that, while all isotopes of a given
element have the same number of protons in
each atom, they differ in neutron number.

14. There are many types of uranium:
U 235
92 U 238
92
A 235
Z 92
Number of protons 92
Number of neutrons 143
A 238
Z 92
Number of protons 92
Number of neutrons 146
Isotopes of any particular element contain the same
number of protons, but different numbers of neutrons.

15. Most of the isotopes which occur naturally are stable.
A few naturally occurring isotopes and all of the man-made
isotopes are unstable.
Unstable isotopes can become stable by releasing
different types of particles.
This process is called radioactive decay and the
elements which undergo this process are called
radioisotopes/radionuclides.

16. Radioactive Decay
• Radioactive decay, also known as nuclear decay or
radioactivity, is the process by which a nucleus of an unstable
atom loses energy by emitting particles of ionizing radiation.
A material that spontaneously emits this kind of radiation—
which includes the emission of energetic alpha particles, beta
particles, and gamma rays—is considered radioactive.

17. Radioactive Decay
Radioactive decay results in the emission of either:
• an alpha particle (a),
• a beta particle (b),
• or a gamma ray(g).

18. Alpha Decay
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.

19. Alpha Decay
X A
Z Y A - 4
Z - 2 + He 4
2
unstable atom
more stable atom
alpha particle

20. Alpha Decay
Ra 226
88
Rn 222
86
He 4
2

21. Beta Decay
Beta decay is one process that unstable atoms can use to
become more stable. There are two types of beta decay,
beta-minus and beta-plus.
During beta-minus decay, a neutron in an
atom's nucleus turns into a proton, an electron and
an antineutrino.

22. Beta Decay
During beta-plus decay, a proton in an atom's nucleus
turns into a neutron, a positron and a neutrino.

23. Gamma Decay
Gamma rays are not charged particles like a and b
particles.
Gamma rays are electromagnetic radiation with high
frequency.
When atoms decay by emitting a or b particles to form a
new atom, the nuclei of the new atom formed may still
have too much energy to be completely stable.
This excess energy is emitted as gamma rays (gamma ray
photons have energies of ~ 1 x 10-12 J).

24. The activity of a radioactive sample is the rate at which atoms decay.
If N(t) is the number of atoms present at a time t, then the activity R is
R = - dN .
dt
dN/dt is negative, so the activity is a positive quantity.
The SI unit of activity is the becquerel: 1 becquerel = 1 Bq = 1 event/second.
Another unit of activity is the curie (Ci) defined by
1 curie = 1 Ci = 3.70x1010 events/s = 37 GBq.

25. 12.2 Half-Life
Experimental measurements show that the activities of radioactive samples fall off
exponentially with time.
*Empirically:
R = -R e -λt
.
0 l is called the “decay constant” of the decaying nuclide. Each radioactive nuclide has
a different decay constant.
*Argh!

26. The half-life , T½, is the time it takes for the activity to drop by ½. We can find a
relationship between l and T½:
R = -R e
2
0 -λΤ 1/2
0
activity after T original activity ½
1 = e-λΤ 1/2
2
e+λΤ 1/2 = 2
( ) 1/2 lΤ = ln 2
( )
1/2 1/2
ln 2 0.693 = =
Τ Τ
l

27. Here's a plot of the activity of a radionuclide.
The initial activity was chosen
to be 1000 for this plot.
The half-life is 10 (in whatever
time units we are using).
All decay curves look like this; only the numbers on the axes will differ, depending on
the radionuclide (which determines the half-life) and the amount of radioactive
material (which determines the initial activity).