The paper presents IUE and optical observations of the Orion Nebula and of the planetary nebula IC 418. Based on these data, log C = 8.5, log O = 8.6 and log N = 7.7 for the Orion Nebula, and log C = 9.0, log O = 8.7 and log N = 7.9 for IC 418 are obtained. These results imply that: (1) lambda-4267 is produced mainly by recombination and provides a reliable method to determine the C(2+) abundance, (2) the Orion nebula has a C/O ratio similar to the solar one, and (3) planetary nebulae show freshly made carbon in their envelopes.
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Torres‐Peimbert et al. (1980) studied this question.