The rotational and tunneling spectrum of the H₂S·CO ₂ van der Waals complex

The rotational spectra of H₂S·CO₂ and two deuterated forms have been observed using a pulsed-beam Fourier-transform microwave spectrometer. For each of the three complexes we assign a-type and c-type transitions which are split into a "weak" and a "strong" intensity component. The analysis based on that previously used for the (H₂O)₂ complex and modified for application to H₂S·CO₂, allowed us to assign internal rotation, inversion tunneling states of the H₂S and CO₂ units in the complex. The following rotational constants were determined for the ground tunneling state of each species: for H₂S·CO₂, A = 11 048.0(26) MHz, B = 2147.786(4) MHz, and C = 1806.468(4) MHz; for HDSCO ₂, A = 10 769(35) MHz, B = 2107.26(24) MHz, and C= 1775.83(24) MHz; and for D₂S·CO₂, A = 10 356.2(28) MHz, B = 2065.376(8) MHz, and C = 1746.122(8) MHz. The electric dipole moments were determined for the H₂S·CO₂ and D ₂SCO₂ species, resulting in the values μ_u = 0.410(14) D and μ_c = 0.822 (10) D for the H₂S· CO₂ species. The structure of the complex has the CO₂ and the S atom of H₂S in a T-shaped configuration. The H₂S plane is nearly orthogonal to the CO₂-S plane with an angle of about 92° and the H₂S·CO₂ center-of-mass separation R_c.m. is 3.498(3) Å.