Gas-phase Binding Energies Research Articles

Analysis of Pulsed Excimer Laser Ablation of PZT, Pb And Ti in an Oxygen Ambient Using Energy Dispersive Mass Spectrometry

AbstractA number of factors have been identified as affecting the gas phase oxidation of cations during pulsed laser ablation of lead zirconate titanate (PZT), by using energy dispersive mass spectrometry (EDMS). These phenomena are known to be critical to the deposition of high quality thin films of PZT. However, to isolate the role of each cation species and the influence of its gas phase properties, we have also looked beyond the ablation of the PZT ceramic. In this paper, we detail our observations during pulsed laser ablation of electroceramic and metallic targets, specifically PZT, Pb and Ti. We have observed the evolution and transport of molecular species during gas phase expansion over a wide range of oxygen pressures (10−7 - 10−1 mbar) and laser fluences (0.3 -10 Jcm−2). The yields of the molecular ion species are strongly dependent upon the number density of the background gas. We propose an interpretation of the relative yields of the species based upon their respective gas phase binding energies and their ease of formation based upon the reaction thermodynamics and reaction cross-section of each species.

Chlorine and hydrogen chloride on clean and oxygen-covered Fe(100): Bonding and reactions

An ASED molecular orbital study of the binding, structures, and reactions of Cl, Cl2, HCl, and HCl+O on 4–21 atom clusters in the Fe(100) structure has been made. Cl2 bonds dissociatively (as seen by Dowben and Jones in LEED and TDS studies). Coverage is limited by σ*p repulsions; orbitals of this symmetry are occupied by electron donation from iron. We find Cl favors onefold and twofold sites and discuss this unexpected result with perturbation theory. It is suggested that with decreased backbonding from iron to Cl the fourfold site can become favored. There is an absence of experimental or theoretical evidence supporting orbital reoccupations to favor the high-coordinate site. HCl dissociation is found to occur with a barrier on the surface that is roughly half the gas phase binding energy, leading to stable products. The HCl+O→Cl+OH reaction on the surface is found to be structure sensitive and the reasons are interpretable from molecular orbital theory.

Interaction of ethene, 2-methylpropene and benzene with the Na + ion. II. Quantum chemical study of sorption complexes in faujasites

The charge distribution obtained by semiempirical quantum chemical methods for the clusters Na+[Si5AlO6H12]−, Na+[Si3Al3O6H12]3−, Na+[Si5AlO18H12]− and Na+[Si3Al3O18H12]3−, representing SII sites in Na-Y and NA-X zeolites, and for Na+[Si4Al4O14H12]4−, representing SIII site, as well as for the corresponding cation free clusters is discussed critically and comparison is made with previous results. The interaction of ethene and 2-methylpropene with the molecular cluster models for SII Na+ sites and the interaction of benzene with models for SII and SIII Na+ sites is considered on the basis of CNDO/2 quantum chemical calculations. The hydrocarbons are found to interact in a π-complex-like structure with the Na+ ions in Na-Y zeolites. The interaction energy is about 65% of the corresponding gas phase binding energy. These results fit in with the experimental information available.

Gas-phase binding energies and spectroscopic properties of nitrosyl(1+) charge-transfer complexes

Gas-phase binding energies and spectroscopic properties of nitrosyl(1+) charge-transfer complexes