Spectroscopic investigations on the HCl(X2Π) ion using coupled-cluster theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions

Abstract

The coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions (aug-cc-pV5Z) is used to investigate the spectroscopic properties of the HCl+(X2Π) ion. The accurate potential energy curve is calculated over the internuclear separation range from 0.051 to 2.51 nm and is fitted to the analytic Murrell-Sorbie function, which is used to accurately determine the spectroscopic parameters such as D0, De, ωeχe, αe, and Be. The present D0, De, Re, ωe, ωeχe, αe, and Be values are of 4.6316, 4.7964 eV, 0.13157 nm, 2684.463, 53.116, 0.3165, and 9.9412 cm−1, respectively, which conform almost perfectly with the available measurements. With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory, a total of 26 vibrational states have been predicted for the first time when the rotational quantum number J is set equal to zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion with the Numerov method. The complete vibrational levels, classical turning points, inertial rotation, and centrifugal distortion constants are reproduced from the potential of the HCl+(X2Π) ion when J = 0 for the first time, which are in excellent agreement with the available experiments. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010