Volume 113, Issue 18, 08 November 2000
Index of content:
113(2000); http://dx.doi.org/10.1063/1.1322657View Description Hide Description
We have explored the deposition of size-selected clusters onto the graphitesurface (at room temperature) over the impact energy range of 250–2500 eV, via a combination of scanning tunneling microscopy experiments and molecular dynamics simulations. We show that the clusters are pinned to the surface when the impact energy exceeds a critical value, which is proportional to the cluster size, N, via the formation of a point defect at the impact site. This prevents lateral diffusion of the clusters even at room temperature.
113(2000); http://dx.doi.org/10.1063/1.1321771View Description Hide Description
Applying the velocity map imaging technique Penning ion formation as well as generation of associative ions is observed in autoionizing collisions of metastable neon atoms with ground state argon targets in a crossed molecular beam experiment. Metastable neon reactants are obtained by nozzle expansion through a dc discharge ring. The quality of the obtained results clearly demonstrates the suitability of this new, particularly straightforward experimental approach with respect to angle and kinetic energy resolved investigations of Penning processes in crossed-beam studies which are known to provide the highest level of detail.
113(2000); http://dx.doi.org/10.1063/1.1323256View Description Hide Description
The new highly accurate complete basis set model, CBS-QB3, was employed here to elucidate the long experimentally discussed problem in a general class of chemiluminescent reactions involving peroxyoxalate systems. Both the stability comparison and the vibrational spectra favor that the intermediate is better to be recognized as the cyclic singlet 1,2-dioxetanedione with the symmetry, which verifies the experimental suggestion yet provides more characterization information. Another two kinds of minimum species in its potential energy surface (PES) are two kinds of product: (1) two carbon dioxide and (2) two carbon monoxide and one oxygen, where the thermodynamic parameters correctly identify their relative yield in the experiment—the former is much more abundant than the latter. In a complete search of minimum states in its PES, the triplet and states were found, which is energetically unfavorable compared with the singlet state. Their vibrational data also support some experimental conclusions of ruling out a radical intermediate. In contrast, the singlet state was found to be a transition state for the “up” and “down” singlet states. The complete active space self-consistent-field calculations with the second-order Möller–Plesset correlation energy correction also support that the most stable species is the singlet state and the singlet state is more energetically favorable than its triplet counterpart.