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abstraction > mathematical concept > number > quantity > radiation measurement > spectral feature > spectral line > emission line > forbidden line

forbidden line (nebular line)
subject			fact

forbidden line	has synonym nebular line
	has definition Spectral line emitted from a metastable state (q.v.), or those which have a very low probability (10-9-10-10) of occurrence. They appear at particle densities ≤ 108 cm-3. All forbidden lines have low excitation potentials. Forbidden lines are designated by enclosing them in brackets, e.g., [O II].
	is a kind of emission line
emission line	has antonym absorption line
spectral line	has transition
	has equivalent width
spectral feature	has wavelength
	has width
	occurs in
	has species
radiation measurement	has unit radiation unit
number	has value

Kinds of forbidden line :

• [O III] line (2 kinds, 9 facts)