Doppler broadening

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. L ack 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. E mitting atoms are in motion with a range of speeds Δ ν 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 (1/2mv 2 )= 3/2kT The spreading of the spectral line due to the temperature of the emitting medium is called as thermal Doppler broadening . S preading of the spectral line depends on the frequency, mass of the emitting particles and the temperature.

5. 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. P ebble bed nuclear reactors

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