The Southampton photoelectron group concentrates on the study of short-lived radicals, many of which are of atmospheric importance. The in situ production of these short-lived molecules is not trivial and can involve any combination of microwave discharge (to produce highly reactive atomic species), high temperature vaporization (up to 3000K) and fast atom-molecule reaction. We currently operate two photoelectron spectrometers, designed and built in Southampton, which use a conventional He I (21.22 eV) photon source to study the electronic structure of short-lived reactive molecules and their ionic states.

Recently a third spectrometer has been designed especially for use with the UK Synchrotron Radiation Source at Daresbury Laboratory, Cheshire and ELETTRA at the Sincrotrone Trieste, Italy. Whilst undergoing development in Southampton this spectrometer utilizes a conventional He I photon source, but for a few months a year is transported one of the synchrotron radiation facilities. Synchrotron radiation provides a tunable  alternative to a conventional photon source and allows us to study photoionization of a selected radical as a function of the exciting energy. We are particularly interested in the observation of autoionizing resonances by constant ionic state (CIS) spectroscopy as both a means of probing highly excited neutral states and of identifying photon energies at which a photoelectron envelope may be extended beyond that observed by conventional means.

Prof. J.M.Dyke is head of the photoelectron group while Dr Alan Morris helps coordinate the day to day running of the project and the work of four postgraduate students, Lucia Zuin, Fabrizio Innocenti, Santy De Frutos, and Giacomo Levita. During allocated beam-times the synchrotron project is assisted by Dr John West of Daresbury Laboratories and Dr. Nicola Zema and Dr. Stefano Stranges at ELETTRA.

Laser MPI spectroscopy allows the spectroscopy and dynamics of excited states of radicals and molecular complexes, accessed by one, two or three photon processes to be studied in some detail.


Ab initio calculations
Calculations of Frank-Condon factors of small polyatomic molecules which includes allowance for anharmonicity.
The main objective of this project is to use ab initio molecular orbital calculations combined with Franck-Condon Factor (FCF) calculations to simulate electronic and photoelectron spectra of triatomic and tetraatomic molecules. This is done to support the experimental work in the group to achieve vibrational assignments of the observed bands.

Calculations of the Structure and Stability of Molecular Complex Ions of Importance to Atmospheric Chemistry

Ab initio calculations are used to calculate the minimum energy geometries and vibrational frequencies of ionic molecular complexes. These species have been shown to be of great importance in the understanding of the chemistry involved in the upper atmosphere. Use of the calculated quantities with simple statistical mechanical techniques allows the calculation of  thermochemical properties, such as the enthalpy, entropy, free energy and equilibrium constants for various reactions. It has been demonstrated that in most cases, accuracy equal to that from experimental measurements is achievable. It is hoped to extend the studies from 1:1 bonded complexes such as NO⁺.H₂O to larger 1:n complexes. It has been shown that intracomplex chemistry can occur in the larger complexes, and this is an area of great relevance to the chemistry of the upper atmosphere.

Further to the work on NO⁺(H₂O)_n, related studies are proposed on O₂⁺(H₂O)_n and ion molecule reactions of atmospherically importance such as:

O₂^- + CH₂Cl₂    and    OH^- + CH₂F₂.