High-resolution nonlinear multi-photon laser spectroscopy as a diagnostic probe for isotopes and molecules in biophysical and geochemical applications

Laser wave mixing is presented as a sensitive absorbance-based detection method for very low activity levels of protease enzymes. Trypsin and proteinase K enzyme activities are analyzed using casein protein covalently labeled with multiple fluorescent BODIPY dye molecules. A preliminary detection limit for trypsin is determined to be 6.34 x 10-14 M or 1.51 pg/mL. For anisotropy studies, wave mixing and fluorescence trends have inverse relationships at the onset of catalysis.; Wave mixing is also investigated as a new optical method for the measurement of FRET. The relationship between the wave-mixing signal and FRET is verified using the acceptor/donor pair malachite green and erythrosin B. Resonance energy transfer between a fluorophore and a quencher molecule bound to complimentary oligonucleotide strands is studied to calculate the dye-to-dye distance on a 31-bp curved DNA fragment. The result suggests that there is a direct measurable relationship between the efficiency of resonance energy transfer and the wave-mixing signal.; For the first time, wave mixing is applied to the measurement of analyte species in the inductively coupled plasma atomizer. The use of counter-propagating input beams yields sub-Doppler spectral resolution. Nonlinear optical coherence theory is used to predict and study the intensity and hyperfine profiles of atomic populations in the plasma torch. Wavelength modulation and ion line detection in the ICP are investigated for S/N enhancement.; Laser wave mixing is also presented as an effective technique for kinetic temperature measurement in an atmospheric-pressure RF inductively coupled plasma using the 4s3P2 → 4p3D 3 argon transition probed by a tunable 811.5-nm diode laser. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by simultaneously measuring the line shapes of the sub-Doppler backward phase-conjugate wave-mixing signal and the Doppler-broadened forward-scattering wave-mixing signal.