CCSD(T) intermolecular potential between He atom and ClF molecule: Comparison with experiment

The potential energy surface of the He-ClF complex is calculated using for He atom an efficient basis set of aug-cc-pV5Z augmented with a set of 3s3p2d2 f1g set of midbond functions and aug-cc-pVTZ, aug-cc-pVQZ for Cl and F atoms, respectively, at coupled-cluster with single and double excitations and a noniterative perturbation treatment of triple excitations [CCSD(T)] level. Three local minima are found for the He-ClF that correspond to linear He-Cl-F (collinear) and He-F-Cl (antilinear) configurations and a asymmetric T-shaped structure. The well depths and the equilibrium distances are 63.53 cm(-1) and 3.54 Angstrom (collinear), 41.09 cm(-1) and 3.23 Angstrom (T-shaped) and 33.80 cm(-1) and 3.93 Angstrom (antilinear). Bound states calculations are carried out for the CCSD(T) surface and the sensitivity of the rovibrational levels to the errors of the computed potential energy surface at different configuration regions is discussed. The computed energy levels up to a total angular momentum J=3 are in general accord with experimental data. (C) 2003 American Institute of Physics.