Continous spectra - line spectra - the doppler effect

Capt'n Midnight wrote: »

single atoms have well defined energy levels for that electrons can occupy

when photons move from one level to another the energy difference can be emitted as light / uv / infra red / heat etc. so you get a series of distinct lines - so monoatomic or ionised gases

Yes, I knew this. I even remember doing spectroscopy experiments - where I'm pretty sure, I was able to determine the I can't remember.

Yeah, you get the lines.

But, say if you pump enough electricity through an ionised gas, eventually the lines will disappear and you will get a continuous spectra. Strictly speaking, the lines don't disappear, but you do get a continuous spectra. Like most of the light from the sun is continuous spectra. When we get light from the sun, it's not limited to the lines of hydrogen.

Now I'm not sure what causes the continuous spectra - do excited or free electrons release photons with any old wavelength?

red shift and blue shift moves these lines , but they stay distinct and don't get blurred.

No. I've found out recently in plasma physics - one trick to measure the temperature of the plasma is to watch this Doppler broadening. The velocity of the atoms in the plasma shift the wavelengths of the lines - and the lines broaden.

Red shift and Blue shift, is a shift of either approaching or receding from a continuous spectra. The continuous spectra from stars only appears white for useful evolutionary reasons.

I've been thinking about this. Hot atoms whizzing around - that velocity has to have a shift effect on the emitted wavelengths - I see they use it in plasma physics. I wasn't sure if it caused the continuous spectra we see from something like the sun.

I've also been thinking about this in terms of how wavelengths are absorbed by atoms. If the atom is in motion, that velocity will shift the incoming photon, and if I'm right, the photon will appear either more or less energetic to the atom.

From what I've learned.

The continuous spectra is caused by phonons. That's why it's continuous and increases in intensity with temperature. And it's also the reason the peak frequency increases with temperature - the atoms are moving faster creating phonons with higher frequencies.