Selector for Structural Isomers of Neutral Molecules

Abstract

We have selected and spatially separated the two conformers of 3-aminophenol (${\mathrm{C}}_6{\mathrm{H}}_7\mathrm{NO}$) present in a molecular beam. Analogous to the separation of ions based on their mass-to-charge ratios in a quadrupole mass filter, the neutral conformers are separated based on their different mass-to-dipole-moment ratios in an ac electric quadrupole selector. For a given ac frequency, the individual conformers experience different focusing forces, resulting in different transmissions through the selector. These experiments demonstrate that conformer-selected samples of large molecules can be prepared, offering new possibilities for the study of gas-phase biomolecules.