Theoretical study of the unusual potential energy curve of the A 1Σ+ state of AgH

Abstract

International audienceThe A 1Σ+ potential energy curve of AgH is studied by means of the second-order multistate multireference perturbation theory including the spin–orbit and relativistic effects. The anomalous behavior of the vibrational energy levels observed in experiment is reproduced well by theory. An analysis of the A 1Σ+ wave function shows that at the internuclear distance of 4–6 Å, a partial electron transfer from the 5pz orbital of silver to the 1s1s orbital of hydrogen occurs. This admixture of the ionic-like [core] 4d101s2H configuration occurring in A 1Σ+ due to two avoided crossings, namely X 1Σ+ with A 1Σ+ and A 1Σ+ with C 1Σ+, is found to be responsible for the unusual shape of the A 1Σ+ potential energy curve: the effective potential is a superposition of a Morse-like covalent interaction between Ag and H, and the electrostatic ionic-like interaction between Ag+ and H⎯. We present spectroscopic parameters, vibrational levels, and rotational constants computed for a large number of vibrational levels and observe good agreement with available experimental data. The equilibrium distance agrees within 0.01 Å and the vibrational frequency within 60 cm−1 for the state-specific calculations. Larger relative discrepancy is observed for ωexe, about 30 cm−1, however the non-Morse-like nature of the energy curve makes it impossible to describe the levels only with ω and ωexe,ωexe, so that direct comparison is not well defined

Candidates for direct laser cooling of diatomic molecules with the simplest Σ1−Σ1 electron

“…In general, spectroscopic constants calculated in the present work are consistent with previous experimental and calculated results [28, 31-33, 45, 46]. Compared to ab initio calculations by Witek et al [31,32], our results for the X 1 Σ + and the A 1 Σ + states of AgH are in better agreement with experimentally determined values. To the best of our knowledge, there was no previous ab initio calculation on molecular constants of the b 3 Σ + state of AgH.…”

“…Groundstate vibrational structure of AgH and AgD was studied in both tunable diode laser absorption spectroscopy [29] and Fourier-transform emission spectroscopy [30]. Witek et al first calculated potential energy curves (PECs) of ground and low-lying excited electronic states of AgH using the relativistic all-electron multireference-based perturbation technique [31,32]. In a global direct-potentialfit analysis of UV, IR and microwave spectra of multiple isotopologues, Le Roy et al determined the analytic potential-energy functions and the Born-Oppenheimer breakdown radial functions for the X 1 Σ + and A 1 Σ + states [33].…”

Density Functional Study of H−D Coupling Constants in Heavy Metal Dihydrogen and Dihydride Complexes: The Role of Geometry, Spin−Orbit Coupling, and Gradient Corrections in the Exchange-Correlation Kernel

“…We have averaged the coupling constant with the groundstate nuclear vibrational wave functions for H 2 , HD, and D 2 , respectively, that were calculated in a discrete variable representation (DVR) 70 based on the TZ2P+steep/revPBE potential curve, using an approach similar to one reported in ref 71. With 23 points we obtain zero-point vibration corrected reduced couplings of 31.3 for H 2 , 31.1 for HD, and 30.9 for D 2 , at the TZ2P+steep/revPBE level, i.e., an additional 5% increase over the equilibrium value of 29.9.…”

Probing the structural and electronic properties of AgnH− (n = 1–3) using photoelectron imaging and theoretical calculations

“…Hydride clusters of Group IB metals have been good prototypes to understand the influences of this important effect. [1][2][3][4][5] To understand the adsorption of hydrogen atom on the silver surfaces and to elucidate the origin of unusual chemical activities of small silver particles, silver hydride clusters have attracted great interests for a long time. [6][7][8][9][10][11] As the simplest silver hydride system, AgH has been well studied using spectroscopic and theoretical methods long ago.…”

“…In the subsequent theoretical efforts, strong interactions among the electronic states were used to understand this anomalous behavior. 2,3,[13][14][15][16][17] The bond length and the vibrational frequency of AgH have been experimentally investigated. 18,19 In gas phase, 18 and the vibrational frequency of AgH were 1.618 Å and 1760 cm −1 , respectively.…”