Sodium vapor lamp

  • Thread starter bejoynp
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  • #1
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Hi

Why do we have only sodium spectral lines in the sodium vapor lamp despite the very low concentration of sodium present in the lamp.
 

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  • #2
Borek
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Is there anything else in the lamp that can emit light?
 
  • #3
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In a sodium vapor lamp, there is 99% inert gas (Penning mixture of Argon and Neon) and 1 % Sodium, but in the spectrum, we can see only sodium lines (despite of low concentration) and no argon or neon lines.
 
  • #4
Borek
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What do you know about the Penning mixture?
 
  • #5
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I am sorry, I accidentally mentioned about low pressure sodium vapor lamp. I actually want to know why Xenon or Mercury spectral lines are not present in the spectrum of High Pressure Sodium lamp. The concentration of sodium in the lamp is about 1% or less.
 
Last edited:
  • #6
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There's a few issues, but it really comes down to brightness. Sodium is used because it's emission is concentrated in a narrow visible band, and it's much brighter than usual.

The other lines are impossibly dim in comparison (and there may be some absorption by the bulb itself, as well).
 
  • #7
K^2
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bejoynp, I think if you look up first ionization energies of Sodium and Xenon, you might find a simple explanation.
 

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