Cluster ions dissociation dynamics

Baer T, Booze j and Weitzei KM (1991) Photoelectron-photoion coincidence studies of ion dissociation dynamics. In Ng CY (ed). Vacuum Ultraviolet Photoionization and Photodissociation of Molecules and Clusters. Singapore World Scientific. 

Photo-excited SO2 and SO2 clusters have been observed to undergo a number of excited state and ion-state processes. Ion-state studies have, for example, identified the energy threshold of the ion-state oxygen loss channel of the SO2 monomer and dimer [1], Additionally, studies investigating the metastable decay process of SO2 clusters and mixed S02-water clusters have identified the dissociation pathways and the nature of the charged core of these cationic clusters [2]. The dynamics of oxygen loss of SO2 and SO2 clusters following excitation to the C (2 A ) state, which couples to a repulsive state, have also been studied to determine the influence of the cluster environment on the dissociation process [3]. 

Until now, most studies of dissociation dynamics of metastable cluster ions have been made using a double-focusing mass spectrometry method (Lifshitz et al. 1990 Lifshitz and Louage 1989, 1990 Stace 1986). As discussed herein, the novel technique of reflectron time-of-flight mass spectrometry is a valuable alternative approach to more standard methods. With carefully designed experiments, it is possible to derive both kinetic energy releases and decay fractions for... 

Thus, the apparent stability of a cluster ion in any specific CMS may arise from a combination of one or more of the following factors, such as structural stability, electronic bonding pattern, and dynamics of unimolecular dissociation. 

To date, neural network potentials have been most frequently applied to represent low-dimensional, molecular PESs. Apart from the central role of molecules in chemistry the main reason for this is certainly the comparably simple mapping of the reference points using electronic structure methods. Low-dimensional NN PESs have been constructed for example for the of ground state and excited state PESs and transition dipole moments of the HCl" ion, " for the OH radical in order to calculate the vibrational levels,for Hi " to calculate rovibrational spectra,for the free H2O molecule, for the dissociation of a Si02 molecule, for the HOOH molecule, for the NOCl molecule, for formaldehyde, for the cis-trans isomerization and dissociation dynamics of nitrous add, " for H + HBr, " for the reaction 0H + H2 H20 + H, for the reaction BeH + H2->BeH2 + H, " for small silicon clusters, " for vinyl bromide, to describe the three-body interaction energies in the H2O-... 

C. Brechignac, Ph. Cahusac, J. Leygnier, and J. Weiner, Dynamics of Uni-molecular Dissociation of Sodium Cluster Ions , J. Chem. Phys. 90, 1492 (1989). 

The classical dynamics treatment for CO on Ni 001) yields results which are in qualitative agreement with these findings. Approximately 80% of the CO molecules that eject are found to eject intact, without rearrangement. The formation of NiCO and NuCO clusters have been observed to form over the surface via reactions of Ni atoms and CO molecules. No evidence has been found for NiC and NiO clusters in the calculations. The ion bombardment approach, then, is a very sensitive probe for distinguishing between molecular and dissociative adsorption processes. 

D. Laria and R. Fernandez-Prini, Molecular dynamics study of water clusters containing ion pairs from contact to dissociation, J. Chem. Phys., 102 (1995) 7664-7673. 

Two models for analyte ion formation have been proposed. The older model -which had not had a well-defined name before 2013 and is now proclaimed as Coupled Physical and Chemical Dynamics (CPCD) model - assumes neutral analyte molecules in the expanding plume - regardless of whether the analytes were incorporated in the matrix crystals as neutral species or were quantitatively neutralized by their counterions upon cluster dissociation in the case of precharged incorporated analyte molecules. Subsequent to photoionization of the matrix (Eqs 1.3 and 1.4) and secondary intermolecular matrix reactions leading to the generation of protonated as well as deprotonated matrix ions (Eqs 1.5 and 1.6)... 

Corrales LR (1999) Dissociative model of water clusters. J Chemical Physics 110 9071-9080 Curtiss LA, Halley JW, Hautman J, Rahman A (1987) Nonadditivity of ab-initio pair potentials for molecular dynamics of multivalent transition metal ions in water. J Chem Phys 86 2319-2327 de Leeuw NH, Parker SC, Catlow CRA, Price GD (2000) Proton-containing defects at forsterite (010) tilt grain boundaries and stepped surfaces. Am Min 85 1143-1154 de Leeuw NH, Parker SC (1998) Surface stracture and morphology of calcium carbonate polymorphs calcite, aragonite, andvaterite An atomistic approach. JPhys ChemB 102 2914-2922... 

The polarity of the metal-carbon bond increases upon going down in the periodic table the lithium alkyls have some covalent character and form tetrameric clusters, whereas cesium alkyls are purely ionic. The degree of clusterification of lithium alkyls varies with the nature of the solvent between dimer (LiCHs TMEDA) and hexamer (Li-n-C4H9 cyclohexane), as can be checked by osmometry, NMR and EPR. Li NMR (I =3/2 abundance 92.6%) and Li NMR (I = 1/2 abundance 7.4%) allow to also show the dynamic fluxionahty phenomena around the Li4 tetrahedron, reversible dissociation of tetramers to dimers and ion pairs (contact ion... 

Information derivable from these techniques is of vital importance in the understanding of the atomic, molecular, ionic, solid-state, and electronic processes that occur at the surface and within the bulk of materials. The dynamics of ion and neutral species, as they approach, penetrate, charge-exchange, diffuse, dissociate (molecules and molecular ions), and sputter some of the substrate atoms, molecules, ions, and clusters, provides a wealth of information. Some of this information cannot be obtained by any other means. Although SIMS is now moving out of adolescence into a stage of matnrity, there is stiU much to be learned about the mechanisms and applications of SIMS and SNMS. 

Clustering of a solnte by a small number of solvent molecules allows one more variable for testing our ideas about how properties scale with the number of molecules in the solvation shell.For example, fast ionization of a neat cluster generates an ion in a non-equilibrium environment and is a way to explore the dynamics of ion solvation. Here we consider another aspect of the caging dynamics in a series of experiments a dihalogen ion, solvated by n CO2 molecules, is photoexcited above its dissociation limit. The quantum yield of atomic and molecular ions is determined as a function of n... 

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