A new four-dimensional ab initio potential energy surface and predicted infrared spectra for the He-CS2 complex

We present a new four-dimensional ab initio potential energy surface for He-CS2 that is constructed at the coupled cluster and doubles with noniterative inclusion of connected triple [CCSD(T)] level with augmented correlation-consistent quadruplet-zeta (aug-cc-pVQZ) basis set plus midpoint bond functions. The Q(1) and Q(3) normal modes for the v(1) symmetric stretching vibration and v(3) antisymmetric stretching vibration of CS2 are involved in the construction of the He-CS2 potential. Two vibrationally averaged potentials with CS2 at the vibrational ground and the v(1) + v(3) excited states are generated from the integration of the four-dimensional potential over the Q(1) and Q(3) coordinates. Each potential is found to have a T-shaped global minimum. The radial discrete variable representation/ angular finite basis representation method is employed to calculate the rovibrational states without separating the inter-and intramolecular vibrations. The calculated shift of band origin (0.2270 cm(-1)) agrees well with the experimental value (0.2278 cm(-1)). The frequencies and line intensities of the rovibrational transitions in the v(1) + v(3) region of CS2 for the vdW vibrational ground state are also in good agreement with the observed infrared spectra.