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Theoretical studies of weakly bound systems: Bimolecular cations and matrix-isolated species
Abstract
Two stable molecules, A and B, often form a stable dimer system, AB$\sp+$, when one of the neutral molecules is ionised. In certain regards, these molecules parallel van der Waals molecules except that the ion-dipole or ion-induced dipole forces play a key role. In the first part of this study we attempt to determine the binding energies, equilibrium geometries, and spectroscopic information for certain sub-classes of bimolecular cations at various post Hartree-Fock levels of theory. Firstly, we studied rare gas dimer cations using standard theoretical methods, e.g. various configuration interaction and Moller-Plesset techniques, where extensive comparison with experimental results and with the results of 'benchmark' post Hartree-Fock methods is made. This comparison has the objective of calibrating the methods used before embarking on calculations of other bimolecular cations for which no information is available. This computational methods are used to study a sequence of bimolecular cations consisting of a rare gas atom and a molecular cation. In particular, we considered the following sequence of molecules: NeHF$\sp+$, NeHCl$\sp+$, NeH$\sb2$O$\sp+$, ArHF$\sp+$, ArHCl$\sp+$, and NeH$\sb2$O$\sp+$. On the second part of this study molecular dynamics simulation are used to investigate the trapping of simple spherical species in rare gas matrices at low temperature. The present study examines the nature of the matrix/host material (i.e. crystalline, amorphous, or polycrystalline) and especially explores the site(s) of the trapped species in the matrix. Also of interest is the nature and degree of the matrix distortion near the trapped molecule, and how is the molecular structure affected by the size of the trapped molecule. At the same time, we intend to bring specific structural details of solid state physics to play a major role in the matrix isolation studies, which have primarily devoted little effort to a full characterization of the matrix. The molecular dynamics techniques used seeks to reproduce details of actual experimental deposition methods, i.e. freezing of the sample, slow spray-on deposition, and pulsed deposition.
Subject Area
Physical chemistry|Molecular physics|Condensed matter physics|Chemistry
Recommended Citation
Lopez, Gustavo Edgardo, "Theoretical studies of weakly bound systems: Bimolecular cations and matrix-isolated species" (1992). Doctoral Dissertations Available from Proquest. AAI9233092.
https://scholarworks.umass.edu/dissertations/AAI9233092