Connecting ultrafast molecular dynamics with real-time heat transfer and fluid mechanics: application to hexane, o-dichlorobenzene, and their equimolar mixture

We have performed resonant and off-resonant ultrafast time-domain OHD-OKE measurements of hexane, o-dichlorobenzeneand their equimolar mixture to characterize the femtosecond to picosecond dynamics following optically-induced thermal diffusion.Off-resonant ultrafast measurements allow characterization of timescales of molecular motions of the three systems at equilibrium, whereas the resonant ultrafast measurements probe the liquid-state dynamics under non-equilibrium conditions by selectively exciting each component. At resonance, the pump-power dependence of the ultrafast time-domain signals is measured to characterize the amount of heat generated and the resulting molecular motions on multiple timescales. Ultrafast spectroscopy measurements are performed in the presence of heat conduction, convection, and turbulence. We study how real-time dynamics influences the ultrafast spectroscopy signals, and how the ultrafast spectroscopy measurements inform on the real-time results.