H-to-Si ratio shows no correlation with meteor velocity, but exhibits a clear positive correlation with photometric mass for cometary meteoroids. The amount of hydrogen detected isn’t mainly determined by atmospheric entry effects. Bigger cometary meteoroids retained more volatiles (hydrogen-bearing compounds).
Meteoroids that came from asteroidal sources (rocky parent bodies) showed very low hydrogen signals, even for large masses.
The intensity equation of a spectral line tells us how much light is emitted when atoms or ions transition from a higher energy level to a lower level.
By comparing the intensity of Hα and Si II lines, the researchers calculated the relative abundance of hydrogen vs silicon (H/Si) in the meteor plasma — once they correct for the temperature and atomic constants.
The researchers used the Saha equation which gives the ratio of ionized to neutral atoms at given temperature and electron density in the plasma. (Here to find how much of the total silicon is in the Si II state.)
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