The ultraviolet (UV) range is unmatched by any other spectral range in number of resonance transitions of the elements required for life, H, C, N, O, S, P. At temperatures below 30,000 K, more than 75% of the resonance transitions of the neutral and singly ionized states for these elements are in the 90–320 nm range, with the only exception of nitrogen.
Fraction of resonance transitions of the basic bio-elements observed in the 90-320 nm spectral range.

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Only resonance transitions of neutral and singly ionized species are considered; the percent of transitions in the 90-320nm is marked in violet; green otherwise.
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Resonance transitions from all ionization states are considered; the percent of transitions in the 90-320nm is marked in violet; orange otherwise. As expected, resonance transition corresponding to high ionization states are observed at wavelengths shorter than 90 nm.
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