Multi-photon Molecular Tagging Thermometry with Femtosecond Excitation (FemtoMTT)

Following our earlier report of first Molecular Tagging Velocimetry (MTV) measurement under nonlinear resonant femtosecond excitation in an aqueous flow, we present results of Molecular Tagging Thermometry (MTT) in a simple jet flow using femtosecond excitation. The two-photon absorption process of a phosphorescent supramolecule allows for simultaneous velocity and temperature measurement using a pair of images obtained during the lifetime of the tracer. Results reproduce the tracer temperature response under typical single photon excitation, while providing potential for high rep-rate capabilities for simultaneous velocimetry and thermometry in aqueous flows and eliminating the need for short wavelength UV excitation source and UV optical access in flow facilities.