The vacuum ultraviolet molecular hydrogen laser is evaluated as a selective ion source for analytical mass spectrometry of easily-ionized compounds. The types of compounds ionized below the photon energy of 7.8 eV include polynuclear aromatic hydrocarbons, and many amines and nitrogen-containing heterocycles. The latter two categories encompass a large number of pharmaceuticals and drugs of abuse. H₂ laser photoionization produces parent molecular ions only, for all compounds studied thus far. Selectivity of the threshold photoionization process is very high, as compounds within as little as 0.2 eV above the threshold are completely rejected. The ability of the technique to discriminate against interfering matrix components is demonstrated for both simple synthetic and complex "real world" mixtures. Easily interpreted spectra are obtained from simple extracts of spiked coffee, beer, soy sauce, urine and blood serum. The most important interference is shown to be electron impact ionization arising from acceleration of stray electrons in the ion source. Most of this ionization is caused by low-energy secondaries generated when stray primaries are collected by the ion source electrodes. The primaries are produced mainly by interaction of scattered laser radiation with metal surfaces. This interference can be controlled through proper instrumental design.

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Extensive information can be obtained on wave-particle interactions and wave fields by direct measurement of perturbed ion distribution functions using laser-induced fluorescence (LIF). For practical purposes, LIF is frequently performed on metastable states that are produced from neutral gas particles and ions in other electronic states. If the laser intensity is increased to obtain a better LIF signal, then optical pumping can produce systematic effects depending on the collision rates which control metastable population and lifetime. We numerically simulate the ion velocity distribution measurement and wave-detection process using a Lagrangian model for the LIF signal. The simulations show that optical pumping broadening affects the ion velocity distribution function (IVDF) $f_0(v)$ and its first-order perturbation $f_1(v,t)$ when laser intensity is increased above a certain level. The results also suggest that ion temperature measurements are only accurate when the metastable ions can live longer than the ion-ion collision mean free time. For the purposes of wave detection, the wave period has to be significantly shorter than the lifetime of metastable ions for a direct interpretation. Experiments are carried out to study the optical pumping broadening and metastable lifetime effects, and the results are compared with the simulation in order to validate the Lagrangian model for LIF. It is more generally true that metastable ions may be viewed as test-particles. As long as an appropriate model is available, LIF can be extended to a range of environments.

Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Dec. 14, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Photonics and Plasmas, Department of Electrical and Computer Engineering, University of Alberta." Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 116-125).

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published_or_final_version / Chemistry / Master / Master of Philosophy

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Isotope shifts of twenty-two isotopes of strontium, $ sp{78}$Sr to $ sp{100}$Sr excluding $ sp{99}$Sr, and three isomers of strontium, $ sp{83 rm m,85m,87m}$Sr, have been measured using laser spectroscopy. The nuclear spins, magnetic and quadrupole moments, have been extracted from the data for all odd isotopes. The changes in mean square charge radii have also been evaluated for all isotopes and isomers. / The changes in mean square charge radii, which are compared to the predictions of the droplet model and Hartree-Fock plus B.C.S. calculations, show a pronounced shell effect at the closed neutron shell at N = 50 and a sharp increase at N = 60. The theoretical analysis suggests that the change in mean square charge radii for N = 60, 62 is due to the onset of a large static deformation. For the remaining isotopes, the changes are attributed to a change in size, a change in the predominantly dynamic deformation, and a change in the diffuseness of the nuclear charge distribution.