Resolving Vibrations in a Polyatomic Molecule with Femtometer Precision

TL;DR

This paper demonstrates femtometer-precision measurement of molecular vibrations using time-resolved x-ray absorption spectroscopy, combining experimental data with ab initio simulations to achieve unprecedented spatial resolution in molecular structure dynamics.

Contribution

It introduces a novel approach that combines femtosecond x-ray spectroscopy with theoretical modeling to measure molecular vibrations at femtometer scale.

Findings

Measured vibrational amplitudes of approximately 50 femtometers.

Mapped energy shifts to internuclear distances using ab initio simulations.

Established core-level spectroscopy as a high-precision molecular-structure metrology tool.

Abstract

We measure molecular vibrations with femtometer precision using time-resolved x-ray absorption spectroscopy. For a demonstration, a Raman process excites the A$_{1g}$ mode in gas-phase SF$_6$ molecules with an amplitude of $\approx50$ fm, which is probed by a time-delayed soft x-ray pulse at the sulfur $L_{2,3}$-edge. Mapping the extremely small measured energy shifts to internuclear distances requires an understanding of the electronic contributions provided by a many-body ab initio simulation. Our study establishes core-level spectroscopy as a precision tool for time-dependent molecular-structure metrology.