Probing plasma-chemistry interactions through novel ultrafast nonlinear laser diagnostics

The field of plasma-assisted chemistry is inducing a paradigm shift in optimizing chemical reactions for desired outcomes. In-situ diagnostics are critical to understanding and optimizing plasma induced molecular effects. Ultrafast nonlinear laser spectroscopies can provide non-perturbative, in-operando, probes with time resolution in the picosecond regime. In this talk we discuss recent results from two sets of experiments. First, the opportunity for enhanced control of detonation transitions through plasma treatment of the reactive mixture was studied. Ultrafast coherent Raman scattering and electric field-induced second-harmonic generation for the direct measurement of time-resolved chemical speciation, electric field, and nonequilibrium ro-vibrational molecular energy distributions during plasma-assisted combustion will be discussed. Second, surface sum-frequency generation (SFG) vibrational spectroscopy results on the interfacial structure of water during plasma-water interactions will be presented. Polarization-resolved SFG provides a glimpse of the interfacial molecular response induced by the plasma-water interaction.