Vibrationally excited intermolecular potential energy surfaces and the predicted near infrared overtone (vOH = 2 ← 0) spectra of a H2O–Ne complex

Abstract

The ab initio intra- and inter-molecular potential energy surfaces (PESs) for the H₂O–Ne system that explicitly incorporate the intramolecular overtone state (v_OH = 2) of H₂O are presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory [CCSD(T)-F12] level with an augmented correlation-consistent triple zeta basis set and an additional bond function. The vibrationally averaged three-dimensional intermolecular potentials for |00⁺〉, |02⁺〉, |02⁻〉 and |11⁺〉 are obtained analytically by fitting to the multi-dimensional Morse/Long-range potential function form. These fits to 46 980 points have a root-mean-square (RMS) discrepancy of 0.12 cm⁻¹ for interaction energies less than 1000.0 cm⁻¹. With the vibrationally averaged PESs for the H₂O–Ne, we employed the combined radial discrete variable representation/angular finite basis representation method and Lanczos algorithm to calculate rovibrational energy levels (J = 0–10, n_s ≤ 2). The predicted infrared transitions and intensities of the para- and ortho-H₂O–Ne complex are in good agreement with the available experimental data for |02⁻〉 ← |00⁺〉, |02⁺〉 ← |00⁺〉 transitions. In particular, the RMS discrepancy for |02⁻〉∑^e(0₀₀,0) ← |00⁺〉∑^e(1₀₁,0), including P and R branch patterns, is only 0.045 cm⁻¹, which is comparable with the experimental values. These results will provide reliable theoretical guidance for the future infrared overtone spectroscopy of clusters.