This thesis presents the results of measuring x-rays from thin pure samples of W, Pt, Au, Pb, Th and U using proton beam energies of 2 and 2.5 MeV provided by a Van de Graaff pelletron accelerator. The spectra were measured using a Si(Li) detector attached to both analog and digital signal-processors. Sophisticated spectrum fitting techniques were used to minimize systematic errors introduced by the detector and its preamplifier-signal-processor electronics. The results of the measurements are presented in the form of peak intensity ratios to minimize any contributions from known sources of systematic error. The results are consistent with the predicted production cross-section ratios obtained using Scofield's Dirac-Fock emission rates, Chen and Crasemann's L subshell ECPSSR-Dirac-Hartree-Slater ionization cross-sections, and the revised recommended fluorescence yields and Coster-Kronig probabilities of Campbell. The results from this study will improve the cross-section information used in PIXE analysis databases.