Quantifying the interplay between fine structure and geometry of an individual molecule on a surface

TL;DR

This study combines advanced ESR-STM techniques and ab initio calculations to precisely characterize the fine structure and geometry of a single TiH molecule on a surface, revealing significant anisotropy and orbital effects.

Contribution

It introduces a novel approach integrating ESR-STM and ab initio methods to analyze the structure and dynamics of individual molecules with high precision.

Findings

Large anisotropy of the g-tensor observed

Non-trivial orbital angular momentum identified

Relationship between fine structure and molecular dynamics established

Abstract

The pathway toward the tailored synthesis of materials starts with precise characterization of the conformational properties and dynamics of individual molecules. Electron spin resonance based scanning tunneling microscopy can potentially address molecular structure with unprecedented resolution. Here, we determine the fine structure and geometry of an individual TiH molecule, utilizing a combination of a newly developed mK ESR-STM in a vector magnetic field and ab initio approaches. We demonstrate a strikingly large anisotropy of the g-tensor unusual for a spin doublet ground state, resulting from a non-trivial orbital angular momentum stemming from the molecular ground state. We quantify the relationship between the resultant fine structure, hindered rotational modes, and orbital excitations. Our model system provides new avenues to determine the structure and dynamics of individual molecules.