Trace Chemical Analysis and Molecular Dynamics Utilising Ultraintense Femtosecond Lasers

[摘要] This thesis is presented for the award of a Ph.D in laser and chemical physics. The principal doctrine of the work seeks to investigate the dynamical response of a variety of small molecules (CS2, CO2, N2O, CH3I, etc.) in an intense (typically 10e16 W cm-2) femtosecond (10e-15 s) linearly polarised laser pulse. The resulting ions are detected in a linear time-of-flight (TOP) mass spectrometer. The polarisation vector of the laser light is rotated with respect to the TOP spectrometer axis and the ion yield measured. In this way the preferred direction of ejection of fragment ions can be determined and the mechanisms responsible can be deduced. The other experimental investigation concerns using short-pulse (femtosecond duration) intense laser pulses to sensitively and unambiguously detect molecules of interest (dangerous and environmentally sensitive species). By increasing both the intensity and reducing the duration of the laser light the method, termed femtosecond laser mass spectrometry (PLMS), is shown to be a universal and powerful analytical tool. The sensitivity is achieved via complete ionisation of all species within the ionisation region of the laser pulse and unambiguous identification is achieved via rapid by-passing of dissociative states of the parent species.

[发布机构] University:University of Glasgow

[关键词] Optics, Physical chemistry, Molecular physics