How sodium atoms in lamp are energized to produce light?

Question

In a recent spectroscopy lab I performed for one of my classes we used a Lambda Scientific LLE-1/2 mercury/sodium lamp (to look at the sodium doublet) and a Lambda Scientific LLE-8 hydrogen/deuterium lamp (to look at the hydrogen/deuterium line). I have been trying to find exactly how these lamps excite the atoms inside to produce light but have failed thus far. From what I have been able to find, I believe it is due to collisional excitations. My main question though is whether the atoms are just excited to a higher level before emitting the light we observed or if the atoms were ionized (rather than just being excited to a higher energy level) and the light we observed in the lab was emitted from the electron's subsequent recombination and cascade back to the ground level?

Answer 1

The sodium D lines are from dropping to 3p to 3s levels. source.

So it's de-excitation rather than recombination.

Mmm, they are called D lines for historical reasons. Also here