15min:

KOHSUKE SUMA, WATARU FUNATO, YOSHIHIRO SUMIYOSHI AND YASUKI ENDO, Department of Basic Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.

Although a number of molecular complexes have been studied extensively for a long time, studies on open-shell radical complexes are relatively scarce due to its difficulty of production. Besides, most of them deal with relatively simple rare-gas(Rg)-diatomic systems. We report the first microwave observation of the Rg-open-shell triatomic species, Ar-HO₂. The a-type and b-type transitions of Ar-HO₂ have been observed using Fourier transform microwave (FTMW) and FTMW-millimeter wave double resonance spectroscopy. The r₀ structure of Ar-HO₂ has been determined from the rotational constants by fixing the structure of the HO₂ monomer. The determined molecular structure is cis planar, where the argon atom is attached to the hydrogen atom of HO₂; r₀(ArH) = 2.622Å, and ₀(ArHO)= 153.9^o . r₀(ArH) of Ar-HO₂ is shoter than that of Ar-HO, 2.776Å, indicating that the Ar-HO₂ bond is relatively rigid. In fact, the binding energy of Ar-HO₂, 292cm^-1, calculated by RCCSD(T)/aug-cc-pVTZ + bond function is much larger than that of Ar-HO or other closed-shell Rg-triatomic species. On the other hand, the determined fine and hyperfine structures are almost identical to those of the HO₂ monomer. The large binding energy may be ascribed to the effect of the low-lying first excited state of the HO₂ monomer.