X-ray spectra can be either continuous or characteristic. Continuous spectra consist of radiations of all possible wavelengths emitted when electrons are slowed by the target material. Characteristic spectra consist of definite wavelengths that are emitted when inner shell electrons are ejected from atoms, creating vacancies that are filled by higher shell electrons as they fall. This releases energy in the form of X-rays at wavelengths characteristic of specific elements. Characteristic spectra appear as sharp lines superimposed on the continuous spectrum.

1. X-Ray spectra
Atomic And Molecular Physics
Presented by :NUMAN USAMA KHAN

2. X-Ray:
• X-rays are a very energetic form of electromagnetic radiation that can be
used to take images of the human body.
• X-rays are roughly classified into soft X-rays and hard X-rays.
• Soft X-rays have (short wavelengths of about 10 nanometers).
• Hard X-rays have (wavelengths of about 100 picometer).

3. History of X-rays:
• X-rays were discovered in 1895 by Wilhelm Conrad Röentgen.
For this discovery, Röentgen was awarded the very first Nobel Prize in physics in 1901.

4. X-Ray spectra:
• X-ray output plotted on graph
called spectra.
• X ray spectra are continuous.
• K-line and L-line are called
characteristics.

5. Continuous and characteristic X-ray spectra:
• The spectrum from an X-ray tube contains two distinct parts.
1. Continuous X-ray spectra.
2. Characteristic X-ray spectra.

6.  Continuous X-ray spectra:
• It consists of radiations of all possible wavelengths, from a certain lower
limit to higher values continuously, as in the case of visible light.

7. Continuous X-ray spectra:
Initial energy = 𝐸 𝑜 =
1
2
𝑚𝑣 𝑜
2
Final energy = 𝐸 =
1
2
𝑚𝑣2
Change in energy = hν = hc/ λ =
1
2
𝑚𝑣 𝑜
2 −
1
2
𝑚𝑣2
ℎ𝑣 𝑚𝑎𝑥 =
1
2
𝑚𝑣 𝑜
2
ℎ
𝑐
λ 𝑚𝑖𝑛
=
1
2
𝑚𝑣 𝑜
2

8. Continuous X-ray spectra:
eV = hνmax = hc / λmin
λmin = hc /eV
Putting the values of Planck's constant, speed of light and the charge of the electron.
λmin = 12400/V A0

9. Continuous X-ray spectra:

10.  Characteristic X-ray spectra:
• It consists of definite, well defined wavelengths superimposed on the
continuous spectrum. These spectral lines generally occur in the form of
small groups and are characteristic of the material of the target.

11. Characteristic X-ray spectra:
• In this case fast moving electron knock out the tightly bound electrons even
from the inner most shells (like K, L shells) of the atom.
• when the fast moving electrons knock off one electron from K-Shell and
the vacancy is filled by the nearby electron from the L shell. During this
transition, the energy difference is radiated in the form of X-rays of very
small wave length. This corresponds to Kα line of the series.
• The frequency ν1 of this line is given by the relation (EK - EL) = hν1
• If electron from M shell jumps to the K shell, it gives out Kβ line and so on.

12. Characteristic X-ray spectra:
• If an electron jumps from the M-Shell to the vacant state in L-Shell, it
contributes Lα line
• If the vacancy in L-Shell is filled up by an electron of N shell, it contributes
Lβ line and so on.
• The frequency of radiation depends upon the target material. The X-ray
spectra consists of sharp lines and is the characteristic of target material.
Hence this spectra is known as characteristic spectra.

13. Characteristic X-ray spectra:
• When we draw Kα line, Kβ line
and Lα line . We get the following
curve.

14. Continuous and characteristic X-ray spectra: