Abstract
This thesis describes a combined experimental and theoretical approach towards anion spectroscopy.
Motivated by the rich chemistry occurring in the Earth’s atmosphere, the first part of thesis describes the design, construction and implementation of an improved anion photoelectron spectrometer based on the velocity map imaging (VMI) principle. This instrument was attached to an existing time-offlight mass spectrometer and conventional anion photoelectron spectrometer. When coupled with a tunable laser, the new spectrometer will allow for high-resolution studies similar to the slow-electron velocity map imaging (SEVI) experiments described by Neumark and co-workers. The spectrometer has been constructed, and preliminary tests have been undertaken.
Complementary to the instrument development, a theoretical methodology for the prediction of electron affinities and photoelectron spectra based on the W3-F12 protocol published by Karton and Martin was established. The methodology is applied to methanal-oxide, cis-ethanal-oxide and trans-ethanaloxide yielding electron affinities of 0.57 eV, 0.18 eV and 0.34 eV, respectively. For all of these molecules as well as their anions, total atomisation energies, harmonic frequencies and heats of formation (at 0 K and 298 K) were calculated alongside.
Finally, a relatively inexpensive computational analysis of the anharmonic frequencies and intensities for methanal-oxide resulting from vibrational second-order perturbation theory (VPT2) CCSD(T) calculations with different basis sets were compared against experimental IR data as well as high-level vibrational configuration interaction (VCI) calculations. Surprisingly, the VPT2 calculations are on a par with computationally more expensive vibrational configuration interaction (VCI) calculations and hence the first simulation of a high-level IR spectrum of cis-ethanal-oxide is presented.
Original language | English |
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Qualification | Doctor of Philosophy |
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Publication status | Unpublished - Feb 2015 |