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The vibrational motion of Ar clusters (Ar_n, n=20, 23, 25, 27, and 30) having isomers in a variety of shapes was simulated by the molecular dynamics method. The intensities of the breathing and quadruple spheroidal vibrations following the breathing-mode excitation of the isomers were calculated. It was found that only the breathing vibration was excited in nearly spherical isomers, while significant excitation of the quadruple spheroidal vibration as well as the breathing vibration was observed in nonspherical isomers. The degrees of sphericality of the isomers were assessed by use of their principal moments of inertia. The excitation of the quadruple spheroidal vibration was found to be closely related to the degrees of sphericality of the isomers.

Absolute cross-sections for dehydrogenation of an ethylene molecule onto , Ti_nO⁺ (n = 2−25), , and were measured as a function of the cluster size, n, in a gas-beam geometry at a collision energy of 0.4 eV in an apparatus equipped with a tandem-type mass spectrometer. It is found that (i) the di-dehydrogenation proceeds on and Ti_nO⁺, and the mono-dehydrogenation on , and , (ii) the di- dehydrogenation cross-section increases gradually with the cluster size of and Ti_nO⁺, (iii)the mono-dehydrogenation cross-section increases rapidly above a cluster size of ∼ 18 for , ∼13 and ∼ 18 for , and ∼ 10 for , and (iv) therapid increase of the cross-section for (M = Fe, Co and Ni) occurs ata cluster size where the 3d-electrons start to contribute to the highest occupied levels of . These findings lead us to conclude that the 3d-electrons of lay a central role in the dehydrogenation on .

The present work concerns with roles played by the internal and collision energy in determining the outcome of a collision process between Ni_n⁺ clusters and methanol molecule. The clusters are being generated using a Xe ion sputter source and are mass-selected in ion beam guided system using quadrupole mass spectrometer. Internal energy of these clusters is being controlled by varying the temperature of the cooling He gas, and collision energy by applying an electric field. The resulting products due to collision between these Ni_n⁺ clusters and methanol molecule are mass analyzed and detected by using a combination of an ion conversion dynode and an electron multiplier. These final products exhibit characteristic dependence on the internal energies of the clusters.