Spontaneous polarization of a nonpolar molecule upon photoexcitation (the sudden polarization effect) earlier discussed for 90 degrees-twisted alkenes is observed and calculated for planar ring-fluorinated stilbenes, trans2,3,5,6,2',3',5',6'-octofluorostilbene (tF2356) and trans2,3,4,5,6,2',3',4',5',6'-decafluorostilbene (tF23456). Due to the fluorination, Franck Condon states S-1(FC) and S-2(FC) are dominated by the quasi-degenerate HOMO -1 -> LUMO and HOMO-2 -> LUMO excitations, while their interaction gives rise to a symmetry-broken zwitterionic S-1 state. After optical excitation of tF2356, one observes an ultrafast (-0.06 ps) evolution that reflects relaxation from initial nonpolar ST to long-lived (1.3 ns in n-hexane and 3.4 ns in acetonitrile) polar S-1. The polarity of Si is evidenced by a solvatochromic shift of its fluorescence band. The experimental results provide a sensitive test for quantum-chemical calculations. In particular, our calculations agree with the experiment, and raise concerns about the applicability of the common TDDFT approach to relatively simple stilbenic systems.