The ab initio potential energy surface and spectroscopic constants of HOCl

The potential energy surface of hypochlorous acid, HOCl, has been determined from large-scale ab initio calculations using the coupled-cluster method CCSD(T). with basis sets of quadruple-and quintuple-zeta quality. The effect of core-electron correlation on the calculated structural parameters has been investigated. The vibrational-rotational energy levels of the three isotopic species of HOCl have then been calculated using the variational method and have been further characterized by the spectroscopic constants determined using the perturbational approach. The spectroscopic constants determined, are found to be in excellent agreement with experimental data. (C) 1998 Elsevier Science B.V.