Accurate ground state potential of Cu2 up to the dissociation limit by perturbation assisted double-resonant four-wave mixing

P Bornhauser; M Beck; Q Zhang; G Knopp; R Marquardt; C Gourlaouen; P P Radi

doi:10.1063/5.0028908

Accurate ground state potential of Cu₂ up to the dissociation limit by perturbation assisted double-resonant four-wave mixing

J Chem Phys. 2020 Dec 28;153(24):244305. doi: 10.1063/5.0028908.

Authors

P Bornhauser¹, M Beck¹, Q Zhang¹, G Knopp¹, R Marquardt², C Gourlaouen², P P Radi¹

Affiliations

¹ Paul Scherrer Institute, Photon Science Department, CH-5232 Villigen, Switzerland.
² Laboratoire de Chimie Quantique, Institut de Chimie, UMR 7177, Université de Strasbourg/CNRS, 4, Rue Blaise Pascal - CS90032, 67081 Strasbourg Cedex, France.

PMID: 33380116
DOI: 10.1063/5.0028908

Abstract

Perturbation facilitated double-resonant four-wave mixing is applied to access high-lying vibrational levels of the X ¹Σ_g ⁺ (0_g ⁺) ground state of Cu₂. Rotationally resolved transitions up to v^″ = 102 are measured. The highest observed level is at 98% of the dissociation energy. The range and accuracy of previous measurements are significantly extended. By applying the near dissociation equation developed by Le Roy [R. J. Le Roy, J. Quant. Spectrosc. Radiat. Transfer 186, 197 (2017)], a dissociation energy of D_e = 16 270(7) hc cm^-1 is determined, and an accurate potential energy function for the X ¹Σ_g ⁺ (0_g ⁺) ground state is obtained. Molecular constants are determined from the measured transitions and by solving the radial Schrödinger equation using this function and are compared with results from earlier measurements. In addition, benchmark multi-reference configuration interaction computations are performed using the Douglas-Kroll-Hess Hamiltonian and the appropriate basis of augmented valence quadruple ζ type. Coupled-cluster single, double, and perturbative triple calculations were performed for comparison.