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  • Spectroscopy and Structure of Intermolecular Clusters and Rotational State-To-State Differential Cross-Sections for the HCI-X Collison System

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    Springfield_2005_01Thesis.pdf (14.26Mb)
    Author(s)
    Springfield, James L
    Primary Supervisor
    Knight, Alan
    Year published
    2005
    Metadata
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    Abstract
    One Colour-Resonant Two-Photon Ionisation, coupled with a supersonic expansion was used to study the rotationally cold excited electronic states of the water clusters of ortho-, meta- and para-difluorobenzene. Ground state rotational constants obtained through ab-initio calculations allowed rotational band contour simulations of these species to be performed, elucidating structural and spectroscopic features such as rotational band types, directions of transition dipole moments and excited state geometries. Confidence in the calculated ground state geometries, obtained through successful simulation of the rotational band ...
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    One Colour-Resonant Two-Photon Ionisation, coupled with a supersonic expansion was used to study the rotationally cold excited electronic states of the water clusters of ortho-, meta- and para-difluorobenzene. Ground state rotational constants obtained through ab-initio calculations allowed rotational band contour simulations of these species to be performed, elucidating structural and spectroscopic features such as rotational band types, directions of transition dipole moments and excited state geometries. Confidence in the calculated ground state geometries, obtained through successful simulation of the rotational band contours, provided strength to the credibility of the vibrational frequencies acquired via these calculations. Analysis of ground state dispersed fluorescence spectroscopy utilising these ab-initio (geometry + frequency) optimisation calculations, allowed assignment of the ground state vibrational modes of each species. Furthermore, comparison of the assigned ground state modes with the excited state spectroscopy, affirmed assignment of the low frequency Van der Waals modes along with the higher frequency aromatic ring modes of these cluster species. A novel technique that produces pseudo-selective excitation of ground state aromatic-rare gas cluster ions was used to assign the vibrational transitions of the D3[less than]D0 electronic excitation spectrum of para-Difluorobenzene+-Argonn=1,2. This technique works on the principle of providing varying degrees of excess energy to the ground state of the cluster ion, as well as altering the Franck-Condon factors for excitation to the D3 electronic state. Measurement of the redshifts for each pDFB-R (where R= Ar1, Ar2, Kr1, Kr2) cluster, revealed that the addition of a second rare-gas adatom doubled the redshift, and that Krypton ad-atoms produced a stronger redshift than argon as expected. It was also noted that the addition of a positive charge to the complex increased the redshift of the complexes, in accordance with our expectations. Rotational state-resolved differential cross sections (DCS's) for rotationally inelastic collisions of HCl with Ne, Ar, and Kr at ~545, ~538, and ~526 cm-1 of collision energy, respectively, were measured using velocity-mapped ion imaging. For each rotational state, the observed DCS's were found to be qualitatively similar. As collider mass was increased, the differential cross section became increasingly forward scattered. Calculations suggest that much of this difference is due to kinematic effects, but that the potential energy surface should be slightly more anisotropic for heavier colliders.
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    Thesis Type
    Thesis (PhD Doctorate)
    Degree Program
    Doctor of Philosophy (PhD)
    School
    School of Science
    DOI
    https://doi.org/10.25904/1912/2779
    Copyright Statement
    The author owns the copyright in this thesis, unless stated otherwise.
    Item Access Status
    Public
    Subject
    Intermolecular clusters
    HCI-X collision system
    one colour-resonant two-photon ionisation
    rotational state-resolved differential cross sections
    Publication URI
    http://hdl.handle.net/10072/365402
    Collection
    • Theses - Higher Degree by Research

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