EP/H004378/1 - Travel Grant to perform Photoionisation Studies - Dyke

Molecular radicals are molecules with an unpaired number of electrons in their ground electronic states. Because of this they are highly reactive. They are important in environments such as plasmas, combustion and the earth's atmosphere where because of their reactivity, they are often present in low concentrations. However, they play a major role in controlling the final chemical products and dominant chemical pathways observed in these environments. Ionization energies of molecular radicals, which will be measured in this work, lead to determination of heats of formation of ions and neutral molecule bond dissociation energies which can be used in models of environments such as plasmas, flames and the earth's atmosphere. The production of ions in the earth's atmosphere will be taken as an example:-Radiation from the sun entering the earth's atmosphere consists of a continuous (black-body) distribution as well as several discrete lines. A part of this radiation is sufficiently energetic to ionize molecular radicals in the atmosphere directly (i.e. non-resonantly). Another mechanism of ionisation involves production of a highly excited neutral state (a Rydberg state), above the first ionic limit which can then ionize. Studying these non-resonant and resonant processes in detail is important in terms of understanding the production of ions in different electronic and vibrational states in the earth's atmosphere. Molecular ions produced from molecular radicals are also important in plasmas, combustion and solution, and studying them via spectroscopic means, supported by electronic structure calculations, as proposed in this project helps to understand their structure and properties, and hence behaviour in these environments. In summary, photoionization processes of molecular radicals are of fundamental importance, and find application in a large number of scientific areas, including astrophysics, planetary science, the chemistry of the earth's atmosphere, radiation chemistry, physics and biology. Workers in these fields require ionisation energies and information on electronic excited neutral states and low-lying ionic states, as well as measures of intensities for photoabsorption and photoionization ( relative and absolute cross-sections) over a wide spectral range. This information is particularly useful in computer simulations and modelling of these environments.