Measuring charge distribution of molecular cations by atomic Coulomb probe microscope

TL;DR

This paper introduces a novel atomic Coulomb probe microscope technique using an Ar atom tip to measure charge distributions in gas-phase molecular cations, enabling structural reconstruction and validation against theoretical models.

Contribution

The study presents a new method for directly imaging charge distributions of molecular cations and dimers with atomic resolution, aligning measurements with theoretical calculations.

Findings

Charge distributions of benzene cations match Mulliken calculations.

Structures of benzene dimers are reconstructed from measured potentials.

Different dimer isomers are distinguished by their inter-molecular potentials.

Abstract

Imaging the charge distributions and structures of molecules and clusters will promote the understanding of the dynamics of the quantum system. Here, we report a method by using an Ar atom as a tip to probe the charge distributions of benzene (Bz) cations in gas phase. Remarkably, the measured charge distributions of Bz cation (QH =0.204,QC=-0.037)and dication (QH =0.248,QC=0.0853)agree well with the calculated Mulliken distributions,and the structures of Bz dimer is reconstructed by using the measured charge distributions. The structures of two Bz dimer isomers (T-shaped and PD isomers) can be resolved from the measured inter-molecular potential V(R) between two Bz ions, and the structures of Bz dimer agree well with the theoretical predictions.