TC10		10min11:16

Y. OZAKI, Department of Chemistry, Faculty of Science, Josai University, Sakado, Saitama 350-02, Japan; M. ICHIHASHI, T. KONDOW, Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan; AND K. KUCHITSU, Department of Chemistry, Faculty of Science, Josai University, Sakado, Saitama 350-02, Japan.

\noindent Previously, we analyzed intracluster vibrational motions of Ar_n, n=13--55, clusters by use of molecular dynamics method . It was shown that a number of collective vibrations were excited. The vibrations were assigned to breathing, quadruple spheroidal and quadruple torsional vibrations corresponding to the modes of a dense sphere with the radius of Ar_n and the phonon velocities in solid Ar. Such vibrations were observed for Ar clusters by the energy loss of colliding He atoms . The frequencies of these vibrations were found to decrease with the increasing cluster size, suggesting that these vibrational motions are new physical properties of clusters obeying a scaling law.

\noindent In this work, the motions of Ar atoms and CO₂ molecule in Ar_nCO₂ cluster produced by addition of CO₂ to the surface of Ar_n cluster, are simulated by use of the classical molecular dynamics method. The potential is calculated by overlapping two-body Lennard-Jones potentials, where an anisotropic potential is used for the Ar-CO₂ interaction. By extracting the breathing and quadruple spheroidal vibrations, the frequencies of these modes are calculated to be: e.g., 33 and 20 cm^-1, respectively, for Ar₁₃CO₂. These values are almost identical to those for Ar₁₃. This indicates that the addition of CO₂ causes little effect on the vibration of Ar₁₃ when the CO₂ molecule is on the surface of Ar₁₃. Cluster-temperature and cluster-size dependence of the frequencies will be presented.