Test of quantum chemistry in vibrationally-hot hydrogen molecules

TL;DR

This study performs high-precision measurements of vibrationally excited hydrogen molecules to test the accuracy of quantum chemistry calculations, achieving experimental precision surpassing current theoretical predictions.

Contribution

It provides the most precise experimental data for high vibrational levels of H₂, enabling rigorous testing and validation of quantum chemical models.

Findings

Experimental energies agree well with ab initio calculations.

Experimental accuracy exceeds current theoretical precision.

Results facilitate future improvements in quantum chemical theories.

Abstract

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The $v=12, J=0-3$ rovibrational levels of H$_2$ ($X^1\Sigma_g^+$), lying only $2000$ cm$^{-1}$ below the first dissociation limit, were populated by photodissociation of H$_2$S and their level energies were accurately determined by two-photon Doppler-free spectroscopy. A comparison between the experimental results on $v=12$ level energies with the best \textit{ab initio} calculations shows good agreement, where the present experimental accuracy of $3.5 \times10^{-3}$ cm$^{-1}$ is more precise than theory, hence providing a gateway to further test theoretical advances in this benchmark quantum system.