No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Nonperturbative rates of harmonic generation or frequency mixing and rates of multiphoton ionisation were obtained for atomic hydrogen and for a one-electron model of the negative hydrogen ion, using the Floquet-Sturmian method. The following cases were investigated: elliptically polarised, monochromatic incident field, two-colour incident field with incommensurable frequencies, coherent super position of an incident field and its third harmonic, and superposition of a laser field and a static electric field. For elliptical polarisation, the ellipticity angle of the harmonics differ from the ellipticity of the incident laser and we established that there is an offset angle between the major axis of the incident laser's polarisation ellipse and that of the harmonics generated. The variation is greatest in the plateau region. Resonance-enhanced ionisation was studied when a high frequency field was applied in addition to a fundamental field. In contrast to these changes in the ionisation rate only small variations have been obtained in the harmonic generation rate. Results for frequency-mixing exhibit a difference in the strength of the harmonics, although the behaviour is the same in terms of the length of the plateau and the cut-off order. Also we found a marked change between sum-frequency and difference frequency processes, which depends on the harmonic order. In addition to a strong production of even harmonics, it was found that the variation of the rate of ionisation and harmonic generation in the presence of a static field oscillates as a function of the strength of the latter. In the case of hydrogen, we observed dc-stark shift induced resonance enhancements. The results obtained for H(^-) are in very good agreement with those obtained for two-colour (w, 3w) mixing. We concluded that the application of a static field in general leads to a reduction in the conversion efficiency.

The two well-known approaches to designing combinatorial generation algorithms are the recursive approach and the iterative approach. In this thesis a third design approach using coroutines, introduced by Knuth and Ruskey, is explored further. An introduction to coroutines and their implementation in modern languages (in particular Python) is provided, and the coroutine-based approach is introduced using an example, and contrasted with the recursive and iterative approaches. The coroutine sum, coroutine product, and coroutine symmetric sum constructs are defined to create an algebra of coroutines, and used to give concise definitions of coroutine-based algorithms for generating ideals of chain and forest posets. Afterwards, new coroutine-based variations of several algorithms, including the Steinhaus-Johnson-Trotter algorithm for generating permutations in Gray order, the Varol-Rotem algorithm for generating linear extensions in Gray order, and the Pruesse-Ruskey algorithm for generating signed linear extensions of a poset in Gray order, are given. / Graduate / 0984 / saba@uvic.ca