Theoretical investigations on the HF+(X2Î ) ion using coupled-cluster theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions

The coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the series of the correlation-consistent basis sets in the valence range are employed to investigate the internuclear equilibrium separations, harmonic frequencies and potential energy curves (PECs) of the HF+(X2Π) ion. The PECs are all fitted to the Murrell-Sorbie function, which is used to determine the spectroscopic parameters (De, D0, ωeχe, αe and Be). By comparison with the available experimental data, the PEC obtained at the basis set, aug-cc-pV5Z, is selected to investigate the vibrational manifolds. The present De, D0, Re, ωe, ωeχe, αe and Be values, which are attained at the aug-cc-pV5Z basis set, are of 3.6156 eV, 3.4262 eV, 0.10011 nm, 3105.202 cm−1, 92.2546 cm−1, 0.89146 cm−1 and 17.5771 cm−1, respectively, which are in excellent agreement with the available experimental results. With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory, a total of 20 vibrational states is predicted when the rotational quantum number J is set to equal zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced from the HF+(X2Π) PEC when J = 0 for the first time.