A selector for structural isomers of neutral molecules

TL;DR

This paper demonstrates the separation of neutral molecular conformers using an ac electric quadrupole selector based on their mass-to-dipole-moment ratios, enabling conformer-specific studies of large molecules.

Contribution

It introduces a novel method for spatially separating neutral molecular conformers using an ac electric quadrupole, expanding capabilities for gas-phase biomolecular research.

Findings

Successfully separated two conformers of 3-aminophenol.

Demonstrated conformer-specific transmission in an ac electric quadrupole.

Enabled preparation of conformer-selected samples of large molecules.

Abstract

We have selected and spatially separated the two conformers of 3-aminophenol (C$_6$H$_7$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.