Elucidating Au-C Bonding via Laser Spectroscopy of Gold Monocarbide

TL;DR

This study reports the first observation of gold monocarbide (AuC) using laser spectroscopy, providing detailed spectral data and insights into Au-C bonding relevant for quantum science and theoretical benchmarks.

Contribution

First spectroscopic characterization of AuC, including electronic states, vibrational structure, and bond dissociation energy, advancing understanding of Au-C bonding.

Findings

Recorded optical spectrum of AuC between 400-700 nm.

Assigned electronic excitations and analyzed vibrational and spin-orbit structure.

Determined Au-C bond dissociation energy and provided a molecular orbital explanation.

Abstract

Gold monocarbide (AuC) has been produced and characterized using laser spectroscopy, representing the first reported observation of AuC. We recorded the optical spectrum of gas-phase AuC between 400 nm and 700 nm, assigning excitations from the $\mathrm{X}\,^2\Pi_{1/2}( (2\sigma)^2 (2\pi)^1 )$ ground state to states arising from the $(2\sigma)^2 (3\sigma^\ast)^1 $ and $(2\sigma)^1 (2\pi)^2 $ configurations. Dispersed-fluorescence spectra are used to study the vibrational and spin-orbit structure of the ground state, branching ratios and radiative lifetimes of the excited states, and the Au--C bond dissociation energy. A molecular orbital diagram is used to rationalize the nature of AuC's low-lying electronic states. The data serve as valuable benchmarks of relativistic theory and are relevant to quantum science and precision measurements with cold molecules.