Knowledge Bank

The rotational spectra of the $C2H4-SO2$ and $C6H6-SO2$ dimers have been observed with a FTMW spectrometer. Twenty-eight a and c dipole transitions have been assigned for $C2H4-SO2$. The transitions occur as doublets of unequal intensity. The doublets presumably arise from internal rotation of the ethylene; the splittings are markedly affected by deuteration. The $C2H4$ and $SO2$ planes are more or less parallel separated by 3.51(2) {\AA} $(Rcm$). The dipole moment of the dimer is 1.65(1) D, virtually unchanged from free $SO2$. Twenty-seven a and c dipole transitions have been assigned for the $C6H6-SO2$ dimer. A number of additional transitions occur which are believed to arise from free or nearly free internal rotation states. The $C6H6$ and $SO2$ planes are approximately parallel separated by 3.48(2) {\AA} ($Rcm$). The dipole moment of the complex is 2.05(1) D.