Stokes shift dynamics of ionic liquids: Solute probe dependence, and effects of self-motion, dielectric relaxation frequency window, and collective intermolecular solvent modes

摘要: In this paper we have used a semi-molecular theory for investigating the probe dependence of Stokes shift dynamics in room temperature ionic liquids (ILs) by considering three different but well-known dipolar solvation probes—coumarin 153, trans-4-dimethylamino-4′-cyanostilbene, and 4-aminophthalimide. addition, effects on polar energy relaxation ILs solute motion, frequency coverage (frequency window) accessed dielectric measurements collective IL intermolecular modes (CIMs) at tera-hertz range been explored. Eleven considered above theoretical study. Calculated results show better agreement with recent (fluorescence up-conversion (FLUPS) + time-correlated single photon counting (TCSPC)) experimental results, particularly short times, when CIM contribution to dependent function (ɛ(ω)) is included. This done via assigning missing dispersion an ɛ(ω) mode 30 cm−1. No significant has observed although magnitude dynamic varies dipole moment excited solute. Calculations using measured broader window generate response functions closer experiments. However, average rates predicted same do not differ appreciably, implying over-all validity these measurements. Results presented here indicate that inclusion solvent molecularity wavenumber static correlations ion structure factor improves significantly comparison between experiments over continuum model predictions solvents.