An intramolecular vibrationally excited intermolecular potential energy surface and predicted 2OH overtone spectroscopy of H2O–Kr

Abstract

A new five-dimensional potential energy surface (PES) for H₂O–Kr which explicitly includes the intramolecular 2OH overtone state of the H₂O monomer is presented. The intermolecular potential energies were evaluated using explicitly correlated coupled cluster theory [CCSD(T)-F12] with a large basis set. Four vibrationally averaged analytical intermolecular PESs for H₂O–Kr with H₂O molecules in its |00⁺〉, |02⁺〉, |02⁻〉, and |11⁺〉 states are obtained by fitting to the multi-dimensional Morse/Long-Range potential function form. Each vibrationally averaged PES fitted to 578 points has root-mean-square (RMS) deviations smaller than 0.14 cm⁻¹ and requires only 58 parameters. The combined radial discrete variable representation/angular finite basis representation method and the Lanczos algorithm were employed to calculate the rovibrational energy levels for |00⁺〉, |02⁺〉, |02⁻〉, and |11⁺〉 states of the H₂O–Kr complexes. The calculated |02⁻〉Π^f/e(1₀₁) ← |00⁺〉Σ^e(0₀₀) and |02⁺〉Π^f/e(1₁₀) ← |00⁺〉Σ^e(1₀₁) infrared transitions are in excellent agreement with the experimental values with RMS discrepancies being only 0.007 and 0.016 cm⁻¹, respectively. These analytical PESs can be used to provide reliable theoretical guidance for future infrared overtone spectroscopy of H₂O–Kr.