Why are the lines from a hollow cathode lamp generally narrower than the lines emited by atoms in a flame?

The lines from a hollow cathode lamp are generally narrower than those emitted by atoms in a flame due to the differences in the environments in which the emissions occur. In a hollow cathode lamp, the gas is ionized in a controlled environment, resulting in a well-defined energy level transition and lower pressure, which leads to less Doppler broadening. In contrast, flames have higher temperatures and pressures, causing a greater range of velocities among the emitting atoms, which broadens the spectral lines due to Doppler effects and collisional broadening. This results in broader emission lines from flame sources compared to the sharper lines from hollow cathode lamps.