Isotopic effect in the (2+1) REMPI spectra of 13C-substituted methyl iodide for UV selective dissociation

► The 6s Rydberg states of carbon-substituted methyl iodide were studied by UV light. ► For the v3 hot band, we observed a well-resolved isotope shift of +16 cm−1. ► The peak shape indicates that the band is suitable for enrichment of the lighter isotope.