The optical pump-terahertz probe spectroscopy was used together with ab initio
calculations and molecular dynamics simulations to investigate ultrafast dynamics
following electronic excitation 
of Coumarin 153 and TBNC dyes in polar solvents. By scanning the terahertz waveform 
for different pump-probe delays this experimental technique allows us to obtain
two dimensional spectra directly reflecting the temporal response of the system. 
A distinct signal was obtained for TBNC in chloroform, 2-propanol, and n-butanol,
while no signal was recorded for Coumarin 153 in either of these solvents. We explain the
non-equilibrium signal detected in TBNC solutions 
by the presence of a solid, polycrystalline phase of the dye
resulting from irradiating the solution by intense optical pulses.