The rovibrational spectrum and structure of the weakly bound CO2-CS2 complex

The rovibrational spectrum of the weakly bound complex CO2-CS2 was observed by exciting the asymmetric stretch of the CO2 moiety near 2349 cm-1. The complex was formed by the supersonic expansion of a 1:2 mixture of CO2 and CS2 in helium and had a nonplanar X-shaped structure. The intermolecular distance is 3.392 Å with a dihedral angle of 90°. The band center is located at 2346.5448 cm-1, with ground-state rotational constants of A″ = 0.08590 cm-1, B″ = 0.04634 cm-1, and C″ = 0.03546 cm-1 and centrifugal distortion constants of Dj″ = -1.37 × 10-7 Cm-1, Dk″ = 1.06 × 10-6 Cm-1, and Djk″ = -1.01 × 10-6 cm-1. The excited-state constants are similar to the ground-state constants. A portion of the potential energy surface was modeled through the use of a Buckingham atom-atom potential and a quadrupole-quadrupole electrostatic potential. Calculations for the CO2-CS2 and (CO2)2 complexes produced structures in agreement with experimental results. Although the CO2-CS2 configuration is controlled by the quadrupole-quadrupole interactions, the atom-atom interactions predominantly determine the energy of the dimer. Because the magnitude of the CS2 quadrupole was increased in the electrostatic potential, the structure shifted from nonplanar X-shaped to a planar parallel configuration.