Spectrum Transitions: Spikes or Lines?

[photon79]

If we look at any spectrum the lines are due to the corresponding transitions in sample. And the line widths are due to the uncertainity principle and doppler effect etc, if these effects are absent should these lines be just spikes?

 

[inha]

Yes, in ideal cases the lines would be delta spikes.

 

[Meir Achuz]

If you see a spectral line that means the level decays. Then, due to the properties of a Fourier transform, there must be a line width of at least
\gamma=2\pi/\tau.