Knowledge Bank

So far, complexes containing molecules with ionic bonds have not been studied by microwave spectroscopy. In the case of such complexes, it is interesting to see how the large dipole moment of the constituent molecule contributes to the structure of the complex and what kind of induced effects are observed by complex formation, in comparison to the complexes formed only by molecules with covalent bonds. Especially, when spectroscopic data for complexes with water for such molecules are obtained, they provide valuable information for understanding the solvation process of ionic molecules into water. In the present study, we have studied Ar-NaCl and $H2O-NaCl$ by FTMW spectroscopy. Gaseous NaCl was produced by laser ablation of an NaCl rod, and expanded into vacuum by using Ar as a carrier gas. In the case of the $H2O-NaCl$ complex, a trace amount of water was added to the carrier gas. The observed spectrum of Ar-NaCl was strong enough to analyze complicated hyperfine structures. It was concluded that the Ar-NaCl complex has a linear structure with Ar attached to the Na side. A slightly larger eQq coupling constant than that of free NaCl was obtained for the Na nucleus, indicating there is an induced effect by the complex formation. Because the spectrum of $H2O-NaCl$ was much weaker, we have obtained only the rotational assignment for the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ species at present. According to a preliminary analysis, the complex has a planar structure with the oxygen atom of water attached to the side of NaCl. Observation of other isotopomers and detailed analysis of the hyperfine structures are now in progress to fix the structure and examine if there are some induced effects to the eQq coupling and the NaCl bond length.