THE ROTATIONAL AND TUNNELING SPECTRUM OF THE H2S.CO2 VANDERWAALS 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 μu = 0.410(14) D and μc = 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 Rc.m. is 3.498(3) Å. © 1990 American Institute of Physics.