We observed the time-resolved fluorescence spectra of a hemicyanine dye with no CC double bond and one CC single bond and of a homologous dye with blocked rotamerism of the CC single bond. Using the more rigid dye, we determined the dynamics of resolvation. Taking that reference, we analyzed the dynamics of rotamerism around the CC single bond. We found that the Franck-Condon geometry equilibrates with a polar-twisted rotamer which is deactivated by fast nonradiative decay. The rotamerism occurs during the relaxation of the solvation shell.