Spectral Line Width And Its Factors

Spectral Line Width And Its Factors

A spectral line’s width serves as a gauge for the spectrum of wavelengths or frequencies it contains. The full width at half maximum (FWHM)is known as width of the line at half of its maximum intensity.

Width can be effected by a number of parameters, such as:

Natural Broadening:

This results from the finite duration of excited states in an atom or molecule, which spreads the system’s energy levels and, in turn, spreads the frequencies that are emitted.

Doppler Broadening:

This occurs when the motion of the emitting particles causes the Doppler effect, which causes a shift in the emitted frequencies.

Pressure Broadening:

This occurs when particles collide in a gas, changing the energy levels of the emitting atoms or molecules and, as a result, causing the emitted spectral line to become wider.

Instrumental Broadening:

This occurs when a narrow spectral line appears wider than it actually is due to the measurement instrument’s finite resolution.


The particular system being examined and the circumstances surrounding the measurement will determine the relative contributions of these elements to the width of a spectral line.