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E. Bakes, D. Hudgins, L. Allamandola (NASA Ames), Xander Tielens (Kapteyn Institute, Groningen, Netherlands)
Recent experimental work and quantum chemical calculations concerning positively charged Polycyclic Aromatic Hydrocarbon (PAH) materials has shown that the infrared (IR) fluorescence between 3.3\mum and 12.5\mum from the interstellar medium (ISM) is suggestive of PAH cations rather than neutral PAHs. I have modelled the PAH charge distribution to determine their size, structure and abundance in interstellar regions. I have determined the relative IR band intensities by comparison with astronomical observations. This has elucidated the nature of the emitters and their structural and chemical evolution in the varying physical conditions of the ISM. This work is a synthesis of theory, a highly comprehensive PAH database from the Allamandola Laboratory Group and infrared observations.