The technique uses tuned pulsed or CW lasers, firstly to excite and then to ionise the atom or molecule under study. The ions are then detected by mass spectrometers or ion chambers, which makes the technique isotopically sensitive. The procedure can be applied to many different types of samples, e.g. detection of trace impurities in semiconductors, the detection of minute quantities of radioactive isotopes, trace metals in biological samples and the assay of environmentally sensitive molecules. The group specialises in the detection of explosive materials, the analysis and structures of biomolecules, eg proteins and the analysis of metals and semiconductors. The group has recently developed its interests to include the study of femtosecond mass spectrometry using ultra fast lasers.
Femtosecond chemistry has both fundamental and strategic applications.
In the past, this has been directed principally to the study of Rydberg and autoionisation levels in atoms, but more recently the fragmentation and wavelength-dependent patterns of aromatic and nitroaromatic molecules have been studied. Yag pumped dye lasers are used in pulse mode with BBO frequency doubling crystals to give wavelength coverage between 200-700nm. Time of flight mass spectrometers, of both linear and reflectron types, are used in conjunction with the laser ionisation. A new high brightness argon ion gun has been fitted to the laser mass spectrometer and RIMS and SIMS comparisons will be made for multi-layered samples. The detection of small numbers of molecules, particularly explosives and drugs.