| The feasibility of laser diode (LD) excitation for analytical fluorescence techniques was investigated in this work. The spectral characteristics of single-mode and high-power array laser diodes were examined with a monochromator, a diode array detector, and a fourier transform Michelson interferometer. The tuning of LD wavelength with temperature and electrical current was also studied.;Experiments in frequency doubling of the laser diode were carried out and compared to results predicted by theory. Temperature tuning of the frequency-doubled LD was demonstrated. The frequency-doubled LD was tuned to 403 nm to excite gallium atoms in a graphite furnace, but it proved to have insufficient intensity to produce a detectable amount of gallium atomic fluorescence. The doubled LD was used more successfully to excite molecular fluorescence. Perylene, a polyaromatic hydrocarbon, was detected in hexane at a level of 100 ppb.;Both high-power and single-mode LDs were used to excite rubidium atomic fluorescence. Limits of detection were 2.1 pg in a graphite furnace and 200 ng in a glow discharge. Amplitude and frequency modulation were used to discriminate against emission background.;Molecular fluorescence of the organic dye IR-140 was excited with both types of LDs, in four different instrumental configurations. The first and simplest approach was a compact, inexpensive filter fluorometer which could be made portable. Luminescence was measured with a red sensitive photodiode. In the second configuration, the laser beam was collimated and passed through the cuvette; luminescence was measured with a monochromator and cooled photomultiplier tube. A concentrational detection limit of 10... |
