Doppler braodening of light due to which we observe redshift or blue shift.

1. Doppler Broadening
M.Zeeshan Khalid
09050610-039

2. Introduction
• It is the broadening of the spectral line due to Doppler
Effect of the random thermal motion of the molecules.
• Lack of sharpness in the spectrum line causes the
broadening and is related to the distribution of velocities
of the atoms or molecules.
• Causes red shifted and blue shifted wavelengths

3. • Emitting atoms are in motion with a range of speeds Δν along
the line of sight to the observer then Doppler Broadening is
given as
• For a gas of atoms of mass m at a temperature T, the velocity
dispersion is given by
where k is the Boltzmann constant (1.38 × 10−23 J K−1)

4. Thermal Doppler broadening
• Atoms and molecules move in a haphazard direction with
average velocity is given as (1/2mv2 )= 3/2kT
• The spreading of the spectral line due to the temperature of
the emitting medium is called as thermal Doppler broadening.
• Spreading of the spectral line depends on the frequency, mass
of the emitting particles and the temperature.

6. Doppler broadening on nuclear reactors
• The Doppler effect arises when the temperature of the fuel
changes.
• When the uranium is heated, its nuclei move more rapidly in
random directions, and therefore generate a wider range of
relative neutron speeds.
• Pebble bed nuclear reactors

7. Doppler Broadening
Applications and other causes
• Thermal Doppler broadening
• Causes of velocity distribution
Turbulent motion Accretion disc
• Stark broadening