FTMW AND FTMW-MMW DOUBLE RESONANCE SPECTROSCOPY OF AN OPEN-SHELL RADICAL COMPLEX, $AR-HO_{2}$.
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Date
2004
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Publisher
Ohio State University
Abstract
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, $Ar-HO_{2}$. The a-type and b-type transitions of $Ar-HO_{2}$ have been observed using Fourier transform microwave (FTMW) and FTMW-millimeter wave double resonance spectroscopy. The $r_{0}$ structure of $Ar-HO_{2}$ has been determined from the rotational constants by fixing the structure of the $HO_{2}$ monomer. The determined molecular structure is cis planar, where the argon atom is attached to the hydrogen atom of $HO_{2}; r_{0}(ArH) = 2.622\AA$, and $\theta_{0}(ArHO)= 153.9^{\circ}$. $r_{0}(ArH)$ of $Ar-HO_{2}$ is shoter than that of Ar-HO, $2.776\AA^{a}$, indicating that the $Ar-HO_{2}$ bond is relatively rigid. In fact, the binding energy of $Ar-HO_{2}, 292 cm^{-1}$, 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 $HO_{2}$ monomer. The large binding energy may be ascribed to the effect of the low-lying first excited state of the $HO_{2}$ monomer.
Description
$^{a}$Y. Ohshima, M. Iida, and Y. Endo, J. Chem. Phys. 95, 7001 (1991)
Author Institution: Department of Basic Sciences, Graduate School of Arts and Sciences, The University of Tokyo
Author Institution: Department of Basic Sciences, Graduate School of Arts and Sciences, The University of Tokyo