Knowledge Bank

Recently, we determined hydrogen bond radii for HF, HCl, HBr, HI, HCN, $H2O$ and HCCH, using the accurate structural data available from microwave spectroscopic studies on several B:HX complexes, where B is a hydrogen bond $acceptora$. For $H2S$, the available data is limited compared to other hydrogen bond donors listed above. Hence, a systematic investigation has been started on several $H2S$ complexes. Several transitions have been observed for $Ar-(H2S)2$ and $C2H4-H2S$ complexes. The rotational spectrum of $C2H4-H2S$ complex appears to be a composite of rotational spectra of the hydrogen bonded $C2H4-H2O$ and the van der Waals complex $C2H4-Ar$. Each transition is split in to four with a smaller splitting of about 0.14 MHz and a larger splitting of 1.67 MHz in $(B+C)/2$. The rotational constants for the strongest progression are $A=26(1)$ GHz; $B=1972.88(1)$ MHz and $c=1866.68(1)$ MHz. Assignment of $Ar-(H2S)2$ spectra is in progress. It was realized that the rotational spectrum for $(H2S)2$ complex has not been completely solved $yetb$ and hence a 'revisit' started. Several more progressions have been assigned for this dimer now. The search for deuterated isotopomers was carried out by bubbling $H2S$ through $D2O$ and some new $H2O-H2S$ transitions have been observed. During this talk, rotational spectra of all these complexes will be discussed.