Robert P. Lucht

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We report the realization of vibrational photoacoustic (VPA) microscopy using optical excitation of molecular overtone vibration and acoustic detection of the resultant pressure transients. Our approach eliminates the tissue scattering problem encountered in near-infrared spectroscopy and enables depth-resolved signal collection. The 2nd overtone of the CH(More)
Airborne contaminants, e.g., bacterial spores, are usually analyzed by time-consuming microscopic, chemical, and biological assays. Current research into real-time laser spectroscopic detectors of such contaminants is based on e.g., resonance fluorescence. The present approach derives from recent experiments in which atoms and molecules are prepared by one(More)
Spontaneous Raman scattering and laser-induced fluorescence are combined to perform simultaneous point measurements of major species concentrations, temperature, and hydroxyl radical concentration in turbulent nonpremixed flames. The Raman-scattering data for major species concentrations and temperature characterize the instantaneous, local, collisional(More)
The use of laser-induced fluorescence (LIF) from acetone is becoming increasingly widespread as a diagnostic of mixing processes in both reacting and nonreacting flows. One of the major reasons for its increasing use is that the acetone LIF signal is believed to be nearly independent of pressure because of fast intersystem crossing from the first excited(More)
Simultaneous, planar laser-induced fluorescence (LIF) images of nitric oxide (NO) and acetone have been used to calculate instantaneous quantitative maps of molecularly mixed jet-fluid fraction in an axisymmetric shear layer. In this experiment, NO is seeded into high-purity nitrogen jet fluid and acetone is seeded into air coflow. On mixing at the(More)
A three-laser, coherent anti-Stokes Raman scattering (CARS) technique for the simultaneous acquisition of spectra from two species has been developed. A narrow-band, tunable dye-laser beam is used as one of the CARS pump beams. The frequency spacing between the spectra of the two species can be adjusted by changing the frequency of the dye-laser pump beam,(More)
Mean and instantaneous measurements of pressure, temperature, and density have been acquired in an optically accessible gas cell and in the flow field of an underexpanded sonic jet by use of the high-resolution N(2) coherent anti-Stokes Raman scattering (CARS) technique. This nonintrusive method resolves the pressure- and temperature-sensitive rotational(More)
A dual-pump, dual-broadband coherent anti-Stokes Raman scattering system for simultaneous measurements of temperature and concentrations of N2, O2, and CO2 in reacting flows is demonstrated. In this system pure rotational transitions of N2-O2 and rovibrational transitions of N2-CO2 are probed simultaneously with two narrowband pump beams, a broadband pump(More)
The effects of intensity fluctuations in the frequency-doubled output of a multimode Nd:YAG pump laser on coheren anti-Stokes Raman spectroscopy (CARS) signal generation have been investigated in a crossed-beam, twocolor CARS experiment. Measurements of signal intensity as a function of time delay (small compared with pulse length) in one pump beam show a(More)