Question

The wavelength of a resonant mercury line is λ= 253.65 nm. The mean lifetime of mercury atoms in the state of resonance excitation is τ= 0.15 μs. Evaluate the ratio of the Doppler line broadening to the natural linewidth at a gas temperature T = 300 K.

Answer 1

A short lived state of mean life T has an uncertainty in the energy of** which is transmitted to the photon it emits as natural broadening. Then**

The Doppler broadening, on the other hand, arises from the thermal motion of radiating atoms. The effect is non-relativistic and the maximum broadening can be written as

Note: Our formula is an order of magnitude estimate.