Abstract: Push-pull molecules 4-N,N-dimethylamino-benzylidene-malononitrile (DMABMN) and julolidine-malononitrile (JDMN) have been examined for their nonlinear optical properties and as probes of microviscosity in polymers and other complex systems. In this study we use these two molecules to probe dynamic heterogeneity in room temperature ionic liquid dimethyl-isopropyl-propylammonium bis(trifluoromethylsulfonyl)imide ([Nip311+][Tf2N-]). Time-resolved emission spectroscopy with 25 ps resolution is used to measure decays of DMABMN and steady-state emission spectroscopy is used to measure the quantum yields of DMABMN and JDMN in [Nip311+][Tf2N-] at different excitation wavelengths. Quantum yields of DMABMN and JDMN in conventional solvents are also measured for comparison. Both the averaged life times from time-resolved measurements and the estimated life times from quantum yield measurements show strong dependences on excitation wavelength, which appears to provide conclusive evidence of dynamic heterogeneity in a room temperature ionic liquid.