KCS

We study solvation dynamics of two systems which are a coarse-grained model of room temperature ionic liquids, 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI⁺PF6^-), and all-atom model of acetonitrile with a diatomic solute pair as a probe molecule by performing molecular dynamics simulations. For a diatomic solute pair, two different state of charge distribution are used, a neutral pair (NP) and a ionic pair (IP) with each atom have opposite charge 0.6364e and -0.6364e. We calculate the normalized time-dependent Stokes shift function in a non-equilibrium solvation dynamics simulation, using a concept of isoconfigurational ensemble to explore the effect of structure in solvation dynamics, after Frank-Condon transition from NP to IP and vice versa, especially in case of ΔE_i→f equals to <ΔE_i→f>. ΔE_i→f is defined by difference of total energy of RTIL-solute system, where i and f mean initial and final solute state. We also perform similar simulation in case of red edge condition and to find specific reasons of dynamic heterogeneity of solvation dynamics.