Detailed temporal behavior of laser-excited sodium tracer in nitrogen and application to nitrogen number density measurements at low densities

Picosecond time-resolved four-wave mixing experiments in sodium-seeded flames

Picosecond four-wave mixing experiments have been used to study collisions in a Na-seeded, premixed, methane-air flame. Population gratings are used to measure Na excited-state quenching collision rates, while polarization gratings are used to measure Na ground-state hyperfine coherence randomizing collision rates and overall Na diffusion rates, even though these processes are slower than the excited-state quenching rate.

Laser fluorescence velocimeter

A new technique is described in which fluid flow velocity can be determined using the laser-induced fluorescence (LIF) signal produced by a space and time modulated excitation. The modulated excitation is produced by a crossed-beam probe volume similar to those commonly employed in particle-scattering laser Doppler velocimeters (LDV). The technique relies on a flow-induced variation of the visibility and phase of the fluorescence signal that results from the finite lifetime for fluorescence decay of the excited species. A simple, infinite reservoir model is presented to illustrate the technique and to identify the controlling parameters.