Knowledge Bank

Recently, Raghavendra and Arunan [1] have shown that methane can form a hydrogen bonded complex with $HX$ ($X=F,Cl,OH,SH$), in which $H-X$ points towards the carbon of methane. Microwave spectroscopy has confirmed the structure of $CH4-HF/HCl/H2O$ complexes. No experimental data is available for $CH4$ - $H2S$ complex to the best of our knowledge. Pulsed Nozzle Fourier Transform Microwave Spectrometer has been used to study the rotational spectrum of $CH4$ - $H2S$ complex. Two progressions were observed. Both could be fitted independently to a linear top. The ground state rotational constant is determined to be $B=2683.100(1)MHz$ and the distortion constant to be $DJ=0.09413(9)MHz$. Based on this rotational constant, the intermolecular separation is determined to be $4.136A˚$. The other state has a rotational constant $B=2593.05(1)MHz$ and a negative distortion constant, $DJ=-0.0089(7)MHz$. The negative distortion constant implies rotational - vibrational coupling and the progression arises from some excited internal rotor/torsional state. Experiments are in progress to look for more states and isotopologues of this complex. Details will be presented in the talk. \bigskip 1.Raghavendra et al.\it{Chem. Phys. Lett.}\ 467(2008)37.