Abstract
Perturbation facilitated double-resonant four-wave mixing is applied to access high-lying vibrational levels of the X 1Σg + (0g +) 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 De = 16 270(7) hc cm-1 is determined, and an accurate potential energy function for the X 1Σg + (0g +) 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.
Highlights
The bond energy of a molecule is a fundamental thermochemical quantity in chemistry: it tells us how much energy is released when a bond is made or, alternatively, how much energy is needed to break that bond
Technical details of the Multi-reference configuration interaction (MRCI) method used to obtain the theoretical results presented in this report on the X 1Σ+g ground state of Cu2 are given in Ref. 34
The agreement is reasonably good asymptotically for the potential function obtained from the “N” calculation, which leads to a dissociation energy that is about 300 hc cm−1 larger than the RKR result
Summary
The bond energy of a molecule is a fundamental thermochemical quantity in chemistry: it tells us how much energy is released when a bond is made or, alternatively, how much energy is needed to break that bond. About one decade after the seminal paper of Gilbert Newton Lewis in 1916,1 who suggested that a pair of electrons shared by two atoms is responsible for the formation of a chemical bond, quantum mechanics laid the ground for our understanding of the creation and destruction of molecules,[2,3,4,5,6] which has been continuously refined since . Quantum chemical models in combination with the rapid growth of computing power provide an alternative to experimental determination. Coupled cluster theory combined with geminal basis sets can be considered to be among the most accurate and scitation.org/journal/jcp powerful method to obtain accurate information on the chemical structure and properties of medium sized molecules, when the ground state is essentially single reference, even when late-transition metal atoms are included.[27]
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