Mass-Correlated High-Resolution Spectra and the Structure of Benzene

Mass-correlated rotational alignment spectroscopy resolved the rotational Raman spectra for 5 benzene isotopologues with unprecedented resolution. 13-C isotopologues were characterized at natural abundance. Fitted rotational constants allowed the analysis of effective and equilibrium bond lengths for benzene with sub-m angstrom uncertainties. We found that previously reported experimental structures were wrong by multiple m angstrom, due to unrecognized H/D isotope effects. Our results also refute recent experimental and theoretical literature claims of identical effective C-H and C-D bond lengths in benzene and reveal an isotope effect similar to that in other small molecules.

Automated summary

Mass-correlated rotational alignment spectroscopy was used to resolve the rotational Raman spectra of 5 benzene isotopologues with unprecedented resolution. The study revealed that previously reported experimental structures were incorrect and showed isotope effects on the C-H and C-D bond lengths in benzene.