By combining the selectivity of high-resolution laser spectroscopy wit
h the specificity of hyperfine interactions in zero-field magnetic-res
onance spectroscopy, C-13-containing isotopomers of pentacene have bee
n observed in natural-abundance samples and H-1-containing isotopomers
of penthcene in ''fully'' deuterated samples. Molecules containing tw
o C-13 nuclei or up to four residual H-1 nuclei have been identified.