|dc.contributor.author||O'Connor, Gerard Dean||-|
|dc.description.abstract||The diffuse interstellar bands (DIBs) are a series of more than 500 interstellar absorption features, the carriers of which have remained unidentified since 1919. In order to determine which aromatic chemical species are likely to be carriers of the DIBs, trends observed in the spectroscopic features of polycyclic aromatic hydrocarbon (PAH) species with chromophores ranging from 6 to 17 carbon atoms are considered. These trends are explored for PAHs with differing charge states and multiplicities, for multiple electronic transitions.
Previously unreported electronic transitions of the neutral radicals 1-naphthylmethyl, 2-napthylmethyl, 9-methylanthracene and 1-pyrenylmethyl as well as the 9-methylanthracenium+ and phenalenium+ radical cations and the closed-shell neutral molecule 1H-phenalene were recorded.
The D1 ← D0 transitions of small PAH resonance stabilized radicals (RSRs) are shown to be unlikely to be responsible for the DIBs. The spectroscopic properties of larger PAH RSRs were empirically extrapolated from experimental and computational trends. The vibronic structures of these molecules were assigned.
As the D1 ← D0 transitions of PAH RSRs are weak, techniques were developed to obtain the gas-phase spectra of more intense electronic transitions to higher excited-states by double-resonance spectroscopy. Several strong transitions were observed, which were then assigned using ab-initio and TD-DFT computational methods.
The spectra of PAH radical cations were recorded. The recorded spectra covered a range from the mid infrared to the ultraviolet.
As a result of the work presented, several classes of PAH can now be dismissed as possible carriers of the DIBs. Further avenues of research have been suggested. The role of this work as part of the ongoing search for the carriers of the DIBs will be discussed.||en_AU|
|dc.publisher||University of Sydney||en_AU|
|dc.publisher||Faculty of Science||en_AU|
|dc.subject||Diffuse Interstellar Bands||en_AU|
|dc.subject||Polycyclic Aromatic Hydrocarbons||en_AU|
|dc.title||Electronic Spectra of Aromatic Hydrocarbons: A Deductive Approach to the Diffuse Interstellar Bands||en_AU|
|dc.type.pubtype||Doctor of Philosophy Ph.D.||en_AU|
|Appears in Collections:||Sydney Digital Theses (Open Access)|