Optical Kerr shutter (OKS) measurements were performed in a solution of a mesoionic compound (MIC) in dimethylsulfoxide using 10 ns pulses of broadband noisy light with a coherence time of 160 fs. The results show a light induced birefringence with two main components: an instantaneous one, which follows the laser coherence time, and a sub-picosecond component, with a characteristic time of 560 fs, which is attributed to the birefringence decay due to molecular interactions.